MD Licensing Exam — Questions and Answers

Question 1: A 30-year-old woman has hundreds of colonic polyps discovered on colonoscopy. Her father died of colon cancer at age 40. Genetic testing reveals an APC gene mutation. She is at greatest risk for which condition?

Familial adenomatous polyposis (Correct answer)
Peutz-Jeghers syndrome
Lynch syndrome
Juvenile polyposis syndrome

Correct answer: Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is caused by germline APC mutations, producing hundreds to thousands of adenomatous polyps with nearly 100% lifetime colorectal cancer risk if untreated.

Question 2: A 45-year-old woman undergoes allogeneic stem cell transplant. On day 35, she develops diarrhea, skin rash, and rising bilirubin. What is the most likely complication?

Graft failure
CMV colitis
Acute graft-versus-host disease (Correct answer)
Veno-occlusive disease

Correct answer: Acute graft-versus-host disease

Acute GVHD (typically within 100 days post-transplant) classically affects skin (rash), gut (diarrhea), and liver (hyperbilirubinemia) as donor T cells attack host tissues.

Question 3: A 4-year-old girl has fever, rash, uveitis, and arthritis affecting fewer than 5 joints. ANA is positive. What is the greatest long-term ocular risk?

Scleritis with globe perforation
Chronic anterior uveitis leading to band keratopathy and blindness (Correct answer)
Optic neuritis causing sudden vision loss
Acute posterior uveitis with retinal detachment

Correct answer: Chronic anterior uveitis leading to band keratopathy and blindness

Oligoarticular JIA with ANA positivity carries a high risk of asymptomatic chronic anterior uveitis that can cause band keratopathy, cataracts, and blindness if not screened regularly.

Question 4: A 28-year-old man with hemoglobin SS disease is started on hydroxyurea. Which mechanism accounts for its primary benefit in sickle cell disease?

Reduces blood viscosity by decreasing platelet count
Inhibits sickling by chelating calcium
Blocks sickling by oxidizing HbS
Increases fetal hemoglobin (HbF) production (Correct answer)

Correct answer: Increases fetal hemoglobin (HbF) production

Hydroxyurea induces HbF synthesis, which dilutes HbS within red cells and inhibits polymerization, reducing vaso-occlusive crises.

Question 5: A patient with type 2 diabetes is started on metformin. Which mechanism best explains its glucose-lowering effect?

Increases insulin secretion from beta cells
Blocks glucose absorption in the small intestine
Increases renal glucose excretion
Inhibits hepatic gluconeogenesis via AMPK activation (Correct answer)

Correct answer: Inhibits hepatic gluconeogenesis via AMPK activation

Metformin primarily activates AMPK in the liver, suppressing gluconeogenesis and reducing hepatic glucose output.

Question 6: A patient develops bloody diarrhea after eating undercooked hamburger at a barbecue. Stool culture grows E. coli that does not ferment sorbitol. Which toxin is most responsible for hemolytic uremic syndrome in this setting?

Heat-labile toxin
Cholera toxin
Heat-stable toxin
Shiga toxin (Correct answer)

Correct answer: Shiga toxin

E. coli O157:H7 produces Shiga toxin (Stx1/Stx2) which damages renal endothelium, leading to hemolytic uremic syndrome characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury.

Question 7: A 35-year-old woman develops fever, dysuria, flank pain, and costovertebral angle tenderness. Urine culture grows >100,000 CFU/mL of a gram-negative rod that is oxidase-negative and ferments lactose. Which organism?

Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Escherichia coli (Correct answer)

Correct answer: Escherichia coli

E. coli is the most common cause of uncomplicated pyelonephritis, fermenting lactose (pink colonies on MacConkey agar) and being oxidase-negative, with the P fimbriae mediating renal tropism.

Question 8: A 67-year-old with a 50 pack-year smoking history undergoes low-dose CT screening. A 7 mm solid nodule is found. Per Lung-RADS, what is the recommended follow-up?

Repeat LDCT in 12 months (annual screening)
PET-CT scan immediately
Repeat LDCT in 6 months (Correct answer)
CT-guided biopsy

Correct answer: Repeat LDCT in 6 months

A 7 mm solid nodule in a high-risk screening patient is Lung-RADS 3 (probably benign), warranting a 6-month follow-up LDCT.

Question 9: A patient on broad-spectrum antibiotics develops profuse watery diarrhea. Stool toxin assay is positive for toxin B. Which antibiotic is first-line treatment?

Rifaximin
Vancomycin (oral) (Correct answer)
Ciprofloxacin
Metronidazole (IV)

Correct answer: Vancomycin (oral)

For non-severe Clostridioides difficile infection, oral vancomycin (or fidaxomicin) is now preferred over metronidazole per current IDSA guidelines due to superior cure rates.

Question 10: A 28-year-old woman of Mediterranean descent presents with lifelong mild fatigue. A CBC reveals: Hgb 10.5 g/dL, MCV 65 fL, RBC 5.8 million/µL, and a normal RDW. Iron studies show a serum ferritin of 80 ng/mL and a transferrin saturation of 30%. Which of the following is the most likely diagnosis?

Iron deficiency anemia
Anemia of chronic disease
Sideroblastic anemia
Beta-thalassemia trait (Correct answer)

Correct answer: Beta-thalassemia trait

The patient presents with microcytic anemia (MCV < 80 fL). Key differentiating features point towards thalassemia trait: a markedly low MCV with a disproportionately high RBC count, a normal RDW, and normal iron studies. The Mentzer Index (MCV/RBC) is < 13 (65/5.8 ≈ 11.2), which is highly suggestive of thalassemia trait rather than iron deficiency anemia, where it is typically > 13. Her Mediterranean ancestry also increases the pre-test probability for beta-thalassemia.

Question 11: Which investigation is most specific for diagnosing herpes simplex encephalitis?

CSF HSV PCR (Correct answer)
Serum HSV antibody titer
EEG showing periodic lateralized epileptiform discharges
MRI FLAIR signal in temporal lobes

Correct answer: CSF HSV PCR

CSF HSV PCR has high sensitivity and specificity (>95%) and is the gold standard for diagnosing herpes simplex encephalitis.

Question 12: A 66-year-old guy who has smoked 59 packs over the course of 59 years arrives at the emergency room complaining of a productive cough and worsening chronic shortness of breath. Over the past two weeks, he has also experienced multiple instances of blood-tinged sputum. His son claims that he has seemed hoarser than usual for the last three weeks. He shows soft dispersed rhonchi in both lung fields with a prolonged expiratory phase, along with dense rhonchi in the right mid-lung field, according to a physical examination. An irregular 6-cm tumor in the right middle lobe of the chest, together with accompanying lobar consolidation, is seen on the chest x-ray film. Which of the following would be the strongest indication that the patient has lung cancer that is surgically incurable?

A post obstructive pneumonia
Hemoptysis
Increasing hoarseness (Correct answer)
Worsening dyspnea

Correct answer: Increasing hoarseness

In a patient with a significant smoking history, worsening dyspnea, hemoptysis, and a lung mass, increasing hoarseness is a strong indicator of surgically incurable lung cancer. Hoarseness in this context often signifies involvement of the recurrent laryngeal nerve, which can be compressed or invaded by a tumor in the mediastinum. Recurrent laryngeal nerve paralysis indicates advanced disease that has spread beyond the lung, making surgical resection unlikely to be curative.

Question 13: A 48-year-old with rheumatoid arthritis develops a new pleural effusion. Pleural fluid analysis shows glucose of 18 mg/dL, pH 7.00, LDH 2,100 U/L, and protein 4.8 g/dL. What is the most likely etiology?

Rheumatoid pleuritis (Correct answer)
Chylothorax
Parapneumonic empyema
Malignant effusion

Correct answer: Rheumatoid pleuritis

Rheumatoid pleural effusions characteristically show very low glucose (<30 mg/dL), very low pH, and very high LDH due to immune complex deposition and impaired glucose transport.

Question 14: A 62-year-old male is undergoing surveillance after a curative resection for Stage III colon cancer one year ago. Which of the following tumor markers is most appropriate to monitor for disease recurrence in this patient?

Prostate-specific antigen (PSA)
CA 19-9
Carcinoembryonic antigen (CEA) (Correct answer)
Alpha-fetoprotein (AFP)

Correct answer: Carcinoembryonic antigen (CEA)

Carcinoembryonic antigen (CEA) is the standard tumor marker used for surveillance in patients with a history of colorectal cancer after curative treatment. A rising CEA level on serial testing can be the first sign of disease recurrence and should prompt further imaging and investigation. CA 19-9 is associated with pancreatic cancer, AFP with hepatocellular carcinoma and certain germ cell tumors, and PSA with prostate cancer.

Question 15: A 65-year-old woman presents with bilateral hip pain that worsens with activity and is relieved by rest. X-ray shows joint space narrowing, subchondral sclerosis, and osteophytes. What is the underlying pathology?

Immune complex deposition in the synovium
Synovial proliferation with pannus formation
Progressive loss of articular cartilage with subchondral bone remodeling (Correct answer)
Urate crystal deposition in periarticular tissues

Correct answer: Progressive loss of articular cartilage with subchondral bone remodeling

Osteoarthritis is characterized by progressive articular cartilage degradation leading to subchondral sclerosis, cyst formation, and osteophyte development.

Question 16: A 25-year-old presents with bloody diarrhea 4 days after attending a barbecue. Stool culture grows E. coli O157:H7. Which complication is most feared in this patient?

Pseudomembranous colitis
Hemolytic uremic syndrome (Correct answer)
Toxic megacolon
Intussusception

Correct answer: Hemolytic uremic syndrome

E. coli O157:H7 produces Shiga toxin that damages renal endothelium, causing hemolytic uremic syndrome characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure.

Question 17: Which medication mechanism is responsible for neuroleptic malignant syndrome?

GABA receptor inhibition
Dopamine receptor blockade (Correct answer)
Serotonin receptor agonism
Acetylcholine receptor blockade

Correct answer: Dopamine receptor blockade

Neuroleptic malignant syndrome results from dopamine receptor blockade by antipsychotics, causing hyperthermia, rigidity, and autonomic instability.

Question 18: A 60-year-old with known lung cancer presents with confusion, proximal weakness, and serum sodium of 118 mEq/L. Urine sodium is elevated and urine osmolality is high. What is the mechanism?

Syndrome of inappropriate ADH secretion (SIADH) (Correct answer)
Cerebral salt wasting
Adrenal insufficiency
Nephrogenic diabetes insipidus

Correct answer: Syndrome of inappropriate ADH secretion (SIADH)

SIADH from ectopic ADH production by small cell lung cancer causes dilutional hyponatremia with inappropriately elevated urine osmolality and sodium.

Question 19: Which of the following is NOT a normal physiologic change during pregnancy?

Expanded plasma volume by 40-50%
Decreased systemic vascular resistance
Decreased glomerular filtration rate (GFR) (Correct answer)
Increased cardiac output by 40-50%

Correct answer: Decreased glomerular filtration rate (GFR)

GFR increases by 40-60% in normal pregnancy due to increased renal plasma flow; a decreased GFR would be abnormal and suggests renal pathology.

Question 20: A patient presents with severe mid-epigastric pain radiating to the back, nausea, and vomiting after a heavy meal. Serum lipase is 1,200 U/L. Which is the most common cause of this presentation?

Gallstones and alcohol use (Correct answer)
Medications and autoimmune disease
NSAID use and hypercalcemia
Hypertriglyceridemia and trauma

Correct answer: Gallstones and alcohol use

Gallstones and alcohol use together account for approximately 80% of acute pancreatitis cases, with gallstones being the single most common cause in the US.

Question 21: A 2-year-old boy presents with colicky abdominal pain, vomiting, and currant jelly stools. Ultrasound shows a 'target sign' in the right upper quadrant. What is the diagnosis?

Intussusception (Correct answer)
Malrotation with volvulus
Hirschsprung disease
Meckel's diverticulum

Correct answer: Intussusception

Intussusception is the telescoping of one segment of bowel into another, classically presenting in children aged 6 months to 2 years with the triad of colicky pain, vomiting, and currant jelly stools.

Question 22: A 50-year-old man receiving cisplatin-based chemotherapy develops fatigue with hemoglobin 7.5 g/dL, low reticulocytes, and inappropriately low erythropoietin. The mechanism of his anemia is:

Renal EPO suppression from cisplatin nephrotoxicity (Correct answer)
Iron deficiency from GI bleeding
Hemolysis
Bone marrow suppression

Correct answer: Renal EPO suppression from cisplatin nephrotoxicity

Cisplatin causes nephrotoxicity that impairs renal EPO production, leading to anemia disproportionate to the degree of myelosuppression.

Question 23: Which feature best distinguishes a Todd's paralysis from an acute ischemic stroke?

Elevated blood pressure
Age of the patient
Presence of headache
Gradual resolution over minutes to hours after a seizure (Correct answer)

Correct answer: Gradual resolution over minutes to hours after a seizure

Todd's paralysis is postictal focal weakness that resolves spontaneously within minutes to hours following a seizure.

Question 24: A 35-year-old patient with a known history of HIV, non-adherent to antiretroviral therapy, presents with a new-onset seizure. His CD4 count is 48 cells/µL. A contrast-enhanced MRI of the brain reveals multiple ring-enhancing lesions, primarily located in the basal ganglia. What is the most likely diagnosis?

Progressive Multifocal Leukoencephalopathy (PML)
Cryptococcoma
Primary CNS lymphoma
Cerebral Toxoplasmosis (Correct answer)

Correct answer: Cerebral Toxoplasmosis

In an HIV-positive patient with a CD4 count below 100 cells/µL, the presence of multiple ring-enhancing brain lesions, particularly in the basal ganglia, is highly characteristic of cerebral toxoplasmosis, caused by the reactivation of latent Toxoplasma gondii infection. [26, 27, 38] While primary CNS lymphoma is a key differential, it more commonly presents as a single lesion. Given the classic presentation, empiric treatment for toxoplasmosis is typically initiated. [29]

Question 25: A 40-year-old woman presents with dry eyes, dry mouth, parotid enlargement, and positive anti-Ro/SSA antibodies. A lip biopsy shows focal lymphocytic sialadenitis. What is the diagnosis?

Rheumatoid arthritis with sicca symptoms
Sjögren syndrome (Correct answer)
Mumps
Sarcoidosis

Correct answer: Sjögren syndrome

Sjögren syndrome is diagnosed by the combination of sicca symptoms, anti-Ro/SSA antibodies, and focal lymphocytic sialadenitis on minor salivary gland biopsy.

Question 26: A 35-year-old woman with diffuse systemic sclerosis develops progressive dyspnea. High-resolution CT shows basal-predominant ground-glass opacities and honeycombing. Which antibody is most associated with this pulmonary complication?

Anti-Jo-1
Anti-Scl-70 (anti-topoisomerase I) (Correct answer)
Anti-centromere
Anti-U1 RNP

Correct answer: Anti-Scl-70 (anti-topoisomerase I)

Anti-Scl-70 antibodies are associated with diffuse cutaneous systemic sclerosis and a higher risk of interstitial lung disease.

Question 27: A 72-year-old woman is diagnosed with osteoporosis after a DEXA scan reveals a T-score of -2.8 at the femoral neck. She has no contraindications to standard therapy. Which of the following best describes the mechanism of action of bisphosphonates, the first-line treatment for this condition?

Stimulates osteoblasts to increase bone formation
Increases intestinal calcium absorption and renal calcium reabsorption
Inhibits osteoclast-mediated bone resorption (Correct answer)
Acts as a selective estrogen receptor modulator in bone

Correct answer: Inhibits osteoclast-mediated bone resorption

Bisphosphonates are potent inhibitors of bone resorption. They bind to hydroxyapatite in bone and are taken up by osteoclasts, where they interfere with cellular processes, leading to osteoclast apoptosis. This action reduces the breakdown of bone, allowing for a net increase in bone density. Teriparatide stimulates osteoblasts, raloxifene is a SERM, and parathyroid hormone (in a complex way) and Vitamin D metabolites increase calcium absorption.

Question 28: A 10-year-old girl has hyperextensible skin, hypermobile joints, and easy bruising. Skin biopsy shows abnormal collagen cross-linking. She likely has a defect in which enzyme?

Lysyl hydroxylase
Collagenase
Prolyl hydroxylase
Lysyl oxidase (Correct answer)

Correct answer: Lysyl oxidase

Ehlers-Danlos syndrome (classical type) involves defective lysyl oxidase or collagen genes, impairing collagen cross-linking and resulting in skin and joint laxity.

Question 29: A patient with Cushing's syndrome undergoes a high-dose dexamethasone suppression test and cortisol is suppressed by >50%. What is the most likely source of excess cortisol?

Ectopic ACTH-secreting tumor
Adrenal adenoma
Pituitary corticotroph adenoma (Cushing's disease) (Correct answer)
Adrenal carcinoma

Correct answer: Pituitary corticotroph adenoma (Cushing's disease)

Suppression of cortisol with high-dose but not low-dose dexamethasone indicates a pituitary source (Cushing's disease), as the adenoma retains partial feedback sensitivity.

Question 30: A 40-year-old returns from sub-Saharan Africa with fever, painless facial swelling, and a rapidly moving subconjunctival worm. Which organism causes this?

Wuchereria bancrofti
Dracunculus medinensis
Onchocerca volvulus
Loa loa (Correct answer)

Correct answer: Loa loa

Loa loa (African eye worm) is transmitted by Chrysops flies and characteristically migrates across the conjunctiva, causing transient Calabar swellings; it is endemic to West and Central Africa.

Question 31: A 55-year-old farmer develops a painless black eschar on his forearm after handling imported animal hides. Gram stain of exudate shows large gram-positive rods in chains. Which toxin mediates systemic lethality?

Exfoliative toxin
Alpha toxin (lecithinase)
Pyrogenic exotoxin A
Protective antigen + lethal factor (lethal toxin) (Correct answer)

Correct answer: Protective antigen + lethal factor (lethal toxin)

Bacillus anthracis cutaneous anthrax is caused by its AB-type toxin; protective antigen (PA) binds host cells and delivers lethal factor (a metalloprotease) or edema factor, with lethal toxin being the primary cause of death.

Question 32: A 58-year-old patient with type 2 diabetes and chronic kidney disease (stage 3) is started on an SGLT2 inhibitor. Which of the following best describes the primary renal mechanism by which this class of medication provides renoprotection?

Increasing insulin sensitivity at the level of the podocyte.
Directly inhibiting the renin-angiotensin-aldosterone system.
Promoting the regeneration of damaged renal tubular cells.
Reducing proximal tubular sodium and glucose reabsorption, which restores tubuloglomerular feedback and reduces glomerular hyperfiltration. (Correct answer)

Correct answer: Reducing proximal tubular sodium and glucose reabsorption, which restores tubuloglomerular feedback and reduces glomerular hyperfiltration.

SGLT2 inhibitors block the sodium-glucose cotransporter 2 in the proximal convoluted tubule, increasing urinary excretion of glucose and sodium. The increased sodium delivery to the macula densa restores tubuloglomerular feedback, leading to afferent arteriolar vasoconstriction. This action reduces intraglomerular pressure and corrects the glomerular hyperfiltration that is a key driver of diabetic kidney disease progression.

Question 33: A 63-year-old woman with a major past medical history of breast cancer arrives at the hospital with a three-day history of a sore throat, lethargy, and a petechial rash throughout the anterior abdominal wall and both lower extremities. A white blood cell count of 115.5 cells/ul (normal: 3.5-10.5 cells/ul), of which 77% are blasts, a hemoglobin level of 6.1 g/dl (normal: 12–16 g/dl), and a platelet count of 22,000/ul (normal: 150–400 thousand/ul) are all revealed by laboratory tests. She receives induction therapy while being treated at the hospital. The following statement is true:

Anthracyclines are associated with cardiomyopathy but are there is no association between their use and secondary leukemias
Leukemias associated with prior chemotherapy are associated with an unfavorable prognosis (Correct answer)
All of the above
Prior treatment with doxorubicin (an anthracycline) for breast cancer has increased her risk of developing leukemia (Correct answer)

Correct answer: Leukemias associated with prior chemotherapy are associated with an unfavorable prognosis

The patient's history of breast cancer treated with doxorubicin (an anthracycline) is a significant risk factor for developing secondary acute myeloid leukemia (AML). Anthracyclines are known to be topoisomerase II inhibitors, which can cause DNA damage and lead to specific chromosomal translocations associated with therapy-related AML. This type of secondary leukemia often carries an unfavorable prognosis.

Question 34: A 72-year-old woman presents with acute knee pain and swelling. Synovial fluid shows positively birefringent rhomboid-shaped crystals under polarized light. What is the diagnosis?

Gout
Septic arthritis
Pseudogout (calcium pyrophosphate deposition disease) (Correct answer)
Hemarthrosis

Correct answer: Pseudogout (calcium pyrophosphate deposition disease)

Calcium pyrophosphate dihydrate (CPPD) crystals are positively birefringent and rhomboid-shaped, distinguishing pseudogout from gout's negatively birefringent needle-shaped urate crystals.

Question 35: A 65-year-old presents with back pain, a serum M-spike, and lytic bone lesions on X-ray. CRAB criteria are met. Which bisphosphonate reduces skeletal events in multiple myeloma?

Alendronate
Pamidronate oral
Zoledronic acid (Correct answer)
Etidronate

Correct answer: Zoledronic acid

Zoledronic acid (IV) is preferred over other bisphosphonates for multiple myeloma bone disease due to superior efficacy in reducing skeletal-related events.

Question 36: A 28-year-old man presents with low back pain that improves with exercise, uveitis, and HLA-B27 positivity. X-ray shows sacroiliitis. What is the most likely diagnosis?

Enteropathic arthritis
Ankylosing spondylitis (Correct answer)
Psoriatic arthritis
Reactive arthritis

Correct answer: Ankylosing spondylitis

Ankylosing spondylitis presents with inflammatory back pain, sacroiliitis on imaging, and is strongly associated with HLA-B27.

Question 37: What is the most common type of skin cancer in the United States?

Squamous cell carcinoma
Melanoma
Merkel cell carcinoma
Basal cell carcinoma (Correct answer)

Correct answer: Basal cell carcinoma

Basal cell carcinoma is the most common skin cancer in the US, accounting for approximately 80% of all skin cancers.

Question 38: Eclampsia differs from preeclampsia by the additional presence of:

New-onset grand mal seizures (Correct answer)
Severe proteinuria (>5g/24h)
HELLP syndrome
Placental abruption

Correct answer: New-onset grand mal seizures

Eclampsia is the occurrence of new-onset grand mal (generalized tonic-clonic) seizures in a woman with preeclampsia that cannot be attributed to other causes.

Question 39: A 50-year-old alcoholic presents with confusion, ataxia, and ophthalmoplegia. Which vitamin deficiency is responsible?

Niacin (B3)
Vitamin B1 (thiamine) (Correct answer)
Vitamin B6 (pyridoxine)
Vitamin B12 (cobalamin)

Correct answer: Vitamin B1 (thiamine)

Wernicke's encephalopathy is caused by thiamine (B1) deficiency, presenting with the classic triad of confusion, ataxia, and ophthalmoplegia; treat with IV thiamine.

Question 40: A 55-year-old man with poorly controlled gout has a serum uric acid of 10.2 mg/dL. He has had three attacks in the past year and has a visible tophus on his right ear. Which medication is the preferred urate-lowering therapy?

Colchicine long-term
Probenecid as first-line
Indomethacin as needed
Allopurinol titrated to uric acid goal <6 mg/dL (Correct answer)

Correct answer: Allopurinol titrated to uric acid goal <6 mg/dL

Allopurinol, a xanthine oxidase inhibitor, is first-line urate-lowering therapy for gout; the target serum uric acid is <6 mg/dL (or <5 mg/dL with tophi) to dissolve urate deposits.

Question 41: A 62-year-old man presents with polyuria, polydipsia, and a serum sodium of 154 mEq/L. Urine osmolality is 80 mOsm/kg after water deprivation; it rises to 600 mOsm/kg after desmopressin administration. What is the diagnosis?

Primary polydipsia
Osmotic diuresis
Central diabetes insipidus (Correct answer)
Nephrogenic diabetes insipidus

Correct answer: Central diabetes insipidus

Central diabetes insipidus is confirmed when urine concentrates appropriately after exogenous desmopressin (ADH), indicating the kidney can respond but lacks sufficient endogenous ADH.

Question 42: A patient has hyponatremia with urine osmolality 550 mOsm/kg and urine sodium 60 mEq/L in the setting of recent lung cancer diagnosis. Which syndrome is most likely?

SIADH (Correct answer)
Psychogenic polydipsia
Adrenal insufficiency
Cerebral salt wasting

Correct answer: SIADH

SIADH associated with ectopic ADH production (e.g., small cell lung cancer) causes euvolemic hyponatremia with concentrated urine and high urine sodium.

Question 43: A 30-year-old female is diagnosed with her first episode of genital herpes. Which antiviral medication's mechanism of action relies on initial phosphorylation by a viral-encoded thymidine kinase, making it highly specific for infected cells?

Oseltamivir
Maraviroc
Foscarnet
Acyclovir (Correct answer)

Correct answer: Acyclovir

Acyclovir is a guanosine analog that is selectively effective against herpes simplex virus (HSV) and varicella-zoster virus (VZV). Its selectivity comes from the first step of its activation, which requires phosphorylation by a viral-specific thymidine kinase. [3, 6, 19] Once converted to acyclovir monophosphate, host cell kinases further phosphorylate it to the active triphosphate form, which then inhibits viral DNA polymerase and causes chain termination. [3, 6] Uninfected cells lack this viral enzyme, so the drug remains largely inactive, minimizing toxicity. [19]

Question 44: A 30-year-old man develops urethritis, conjunctivitis, and asymmetric arthritis after a Chlamydia trachomatis infection. Which HLA type is associated with increased risk?

HLA-DR3
HLA-DR4
HLA-B51
HLA-B27 (Correct answer)

Correct answer: HLA-B27

Reactive arthritis (formerly Reiter syndrome) is strongly associated with HLA-B27 and occurs after genitourinary or gastrointestinal infections.

Question 45: Lichen planus is classically described by the '6 P's.' Which set correctly identifies them?

Pruritic, Purple, Polygonal, Planar, Papules, Plaques (Correct answer)
Pink, Pustular, Papillary, Perioral, Pruritic, Progressive
Painful, Papular, Pink, Pruritic, Peripheral, Peeling
Pale, Pigmented, Periungual, Pruritic, Papular, Palmar

Correct answer: Pruritic, Purple, Polygonal, Planar, Papules, Plaques

Lichen planus is described by the 6 P's: Pruritic, Purple, Polygonal, Planar, Papules, and Plaques, often with Wickham's striae on the surface.

Question 46: A 30-year-old woman has episodic hemolysis, pancytopenia, and venous thrombosis. Flow cytometry shows absence of CD55 and CD59 on RBCs. What is the defect?

Spectrin mutation
GPI anchor deficiency (Correct answer)
Pyruvate kinase deficiency
Band 3 protein loss

Correct answer: GPI anchor deficiency

Paroxysmal nocturnal hemoglobinuria (PNH) results from a PIGA mutation causing GPI anchor deficiency, rendering cells vulnerable to complement-mediated lysis.

Question 47: A 25-year-old woman presents with new-onset focal-onset impaired awareness seizures. MRI shows a unilateral medial temporal sclerosis. What is the most likely seizure type?

Mesial temporal lobe epilepsy (Correct answer)
Lennox-Gastaut syndrome
Absence epilepsy
Juvenile myoclonic epilepsy

Correct answer: Mesial temporal lobe epilepsy

Hippocampal sclerosis is the hallmark of mesial temporal lobe epilepsy, the most common focal epilepsy syndrome in adults.

Question 48: A patient with cirrhosis develops acute upper GI bleeding. Endoscopy reveals tortuous, dilated submucosal veins at the gastroesophageal junction. What is the pathophysiologic mechanism?

Aortoenteric fistula formation
Portal hypertension causing portosystemic shunting (Correct answer)
Increased arterial blood flow to the esophagus
Mesenteric ischemia

Correct answer: Portal hypertension causing portosystemic shunting

Portal hypertension from cirrhosis causes blood to shunt through portosystemic collaterals including esophageal varices, which are prone to rupture.

Question 49: A 70-year-old man presents with confusion, polyuria, and blood glucose of 950 mg/dL. Serum bicarbonate is 22 mEq/L and ketones are negative. What is the diagnosis?

Alcoholic ketoacidosis
Diabetic ketoacidosis
Lactic acidosis
Hyperosmolar hyperglycemic state (HHS) (Correct answer)

Correct answer: Hyperosmolar hyperglycemic state (HHS)

HHS presents with extreme hyperglycemia and hyperosmolarity without significant ketoacidosis, typically in elderly type 2 diabetics.

Question 50: Which of the following expressions describes the restriction of comfortable breathing to upright postures?

Eupnea
Dyspnea
Apnea
Orthopnea (Correct answer)

Correct answer: Orthopnea

Orthopnea is a specific type of dyspnea (shortness of breath) that occurs when lying flat, forcing the person to sit or stand up to breathe comfortably. This symptom is often associated with conditions like congestive heart failure, where fluid accumulates in the lungs more easily in a supine position. Apnea is the cessation of breathing, dyspnea is general difficulty breathing, and eupnea is normal breathing.

Question 51: A 28-year-old with cystic fibrosis has FEV1 of 40% predicted and is homozygous for F508del mutation. Which targeted therapy is most appropriate?

Lumacaftor/ivacaftor
Ataluren
Ivacaftor monotherapy
Elexacaftor/tezacaftor/ivacaftor (ETI) (Correct answer)

Correct answer: Elexacaftor/tezacaftor/ivacaftor (ETI)

Elexacaftor/tezacaftor/ivacaftor (Trikafta) is the most effective CFTR modulator for F508del homozygous patients, producing the greatest improvement in FEV1 and sweat chloride.

Question 52: Which of the following best describes the key histopathological change seen in Barrett's esophagus and the primary long-term risk associated with this condition?

Squamous metaplasia; increased risk of esophageal stricture.
Intestinal metaplasia; increased risk of esophageal adenocarcinoma. (Correct answer)
Muscular hypertrophy; increased risk of achalasia.
Glandular hyperplasia; increased risk of esophageal squamous cell carcinoma.

Correct answer: Intestinal metaplasia; increased risk of esophageal adenocarcinoma.

Barrett's esophagus is a complication of chronic GERD characterized by the replacement of the normal stratified squamous epithelium of the esophagus with specialized intestinal metaplasia, which includes goblet cells. This metaplastic change is the most important risk factor for the development of esophageal adenocarcinoma. Squamous cell carcinoma is typically associated with smoking and alcohol, not Barrett's esophagus.

Question 53: Ovarian torsion is most commonly associated with:

An ovarian cyst or mass (typically >5 cm) (Correct answer)
Endometriosis
Pelvic inflammatory disease
Polycystic ovarian syndrome

Correct answer: An ovarian cyst or mass (typically >5 cm)

Ovarian torsion most commonly occurs when an ovarian cyst or mass greater than 5 cm twists the infundibulopelvic ligament, compromising ovarian blood supply.

Question 54: A 70-year-old man with diabetes and CKD stage 3 has an HbA1c of 9.2%. His provider avoids aggressive glycemic targets. What is the primary reason for setting a less stringent HbA1c goal (e.g., <8%)?

Increased risk of hypoglycemia with limited ability to recognize or recover (Correct answer)
Lower cost of medications
Reduced cardiovascular benefit in elderly
Reduced need for monitoring in CKD

Correct answer: Increased risk of hypoglycemia with limited ability to recognize or recover

Elderly patients with CKD have blunted hypoglycemia counterregulation and impaired drug clearance, making tight control dangerous with high hypoglycemia risk.

Question 55: A 72-year-old man presents with acute onset severe abdominal pain out of proportion to physical findings, nausea, and bloody diarrhea. He has a history of atrial fibrillation. CT angiography confirms mesenteric ischemia. Which vessel is most commonly involved?

Inferior mesenteric vein
Celiac artery
Inferior mesenteric artery
Superior mesenteric artery (Correct answer)

Correct answer: Superior mesenteric artery

Acute mesenteric ischemia most commonly results from embolic occlusion of the superior mesenteric artery (SMA), which supplies the small intestine and proximal colon.

Question 56: A 22-year-old male is brought to the emergency department after being found unconscious at a rave. He is diagnosed with rhabdomyolysis secondary to MDMA (ecstasy) use. Which of the following is the primary mechanism by which rhabdomyolysis causes acute kidney injury (AKI)?

Severe dehydration leading to prerenal azotemia.
Direct nephrotoxic effect of the drug on the glomeruli.
Immune-mediated glomerulonephritis triggered by muscle breakdown products.
Renal tubular obstruction by myoglobin casts and direct cytotoxicity of myoglobin. (Correct answer)

Correct answer: Renal tubular obstruction by myoglobin casts and direct cytotoxicity of myoglobin.

In rhabdomyolysis, massive breakdown of skeletal muscle releases large amounts of myoglobin into the circulation. This myoglobin is filtered by the glomeruli but can precipitate in the renal tubules, especially in the setting of dehydration and acidic urine, forming casts that cause physical obstruction. Additionally, the heme component of myoglobin is directly toxic to renal tubular epithelial cells, causing acute tubular necrosis.

Question 57: A 63-year-old male with a 40 pack-year history presents with hemoptysis, weight loss, and a right hilar mass. Biopsy shows small cell lung cancer. Staging workup reveals no distant metastases and disease confined to one hemithorax. What is the standard treatment?

Concurrent cisplatin/etoposide chemotherapy with thoracic radiation (Correct answer)
Immunotherapy with pembrolizumab
Prophylactic cranial irradiation alone
Surgery followed by adjuvant chemotherapy

Correct answer: Concurrent cisplatin/etoposide chemotherapy with thoracic radiation

Limited-stage SCLC is treated with concurrent platinum-based chemotherapy (cisplatin/etoposide) and thoracic radiation, followed by prophylactic cranial irradiation in responders.

Question 58: A 45-year-old with HIV (CD4 count 85 cells/μL) presents with progressive dyspnea, dry cough, and bilateral ground-glass opacities. LDH is elevated. What is the first-line treatment?

Fluconazole
Liposomal amphotericin B
Ganciclovir
Trimethoprim-sulfamethoxazole plus prednisone (Correct answer)

Correct answer: Trimethoprim-sulfamethoxazole plus prednisone

TMP-SMX is first-line for Pneumocystis jirovecii pneumonia (PCP), and adjunctive corticosteroids are indicated when PaO2 <70 mmHg or A-a gradient >35 mmHg.

Question 59: A 50-year-old man with a history of NSAID use presents with sudden onset epigastric pain radiating to the back and a rigid abdomen. Upright chest X-ray shows free air under the diaphragm. What has occurred?

Acute mesenteric ischemia
Acute pancreatitis
Perforated peptic ulcer (Correct answer)
Sigmoid volvulus

Correct answer: Perforated peptic ulcer

Perforated peptic ulcer causes pneumoperitoneum (free air under the diaphragm) and peritonitis, presenting as a surgical emergency with sudden severe epigastric pain and abdominal rigidity.

Question 60: A 55-year-old woman is receiving combination chemotherapy for breast cancer. Which of the following agents is most notoriously associated with a dose-dependent, cumulative cardiotoxicity that can lead to congestive heart failure?

Cisplatin
Methotrexate
Doxorubicin (Correct answer)
Vincristine

Correct answer: Doxorubicin

Doxorubicin, an anthracycline antibiotic, is well-known for causing dose-dependent cardiotoxicity. The risk of developing cardiomyopathy and congestive heart failure increases significantly with higher cumulative doses. Vincristine is associated with peripheral neuropathy, Cisplatin with nephrotoxicity and ototoxicity, and Methotrexate with myelosuppression and mucositis.

Question 61: The Nikolsky sign (skin separation with lateral pressure) is positive in which condition?

Psoriasis
Lichen planus
Contact dermatitis
Pemphigus vulgaris (Correct answer)

Correct answer: Pemphigus vulgaris

The Nikolsky sign is positive in pemphigus vulgaris due to loss of intraepidermal adhesion from autoantibodies against desmoglein.

Question 62: Standard intrapartum prophylaxis against Group B Streptococcus (GBS) neonatal disease uses:

Oral clindamycin
IV ampicillin (Correct answer)
IV vancomycin
IV azithromycin

Correct answer: IV ampicillin

Intravenous penicillin G or ampicillin is the standard intrapartum prophylaxis for GBS-colonized mothers to prevent neonatal early-onset GBS disease.

Question 63: Which Pap smear result in a woman over 25 requires immediate colposcopy?

Negative for intraepithelial lesion
ASCUS with negative HPV co-test
HSIL (high-grade squamous intraepithelial lesion) (Correct answer)
LSIL with negative HPV

Correct answer: HSIL (high-grade squamous intraepithelial lesion)

HSIL on Pap smear requires immediate colposcopy with directed biopsy due to high risk of underlying CIN 2/3 or invasive cervical carcinoma.

Question 64: A patient with type 2 diabetes on metformin has an HbA1c of 8.5%. The provider adds an SGLT2 inhibitor. Which additional benefit beyond glucose control supports this choice in a patient with established cardiovascular disease?

Complete elimination of hypoglycemia risk
Reversal of diabetic nephropathy
Decreased risk of major adverse cardiovascular events (Correct answer)
Reduction in HbA1c by 3%

Correct answer: Decreased risk of major adverse cardiovascular events

SGLT2 inhibitors (e.g., empagliflozin, canagliflozin) have demonstrated significant reduction in MACE and heart failure hospitalization in patients with established CVD.

Question 65: A 58-year-old woman presents with polyarthralgia, malar rash, photosensitivity, and pleuritis. ANA is 1:640 with a speckled pattern. Which antibody is most specific for her condition?

Anti-Ro/SSA
Anti-U1 RNP
Anti-histone
Anti-Smith (anti-Sm) (Correct answer)

Correct answer: Anti-Smith (anti-Sm)

Anti-Smith antibodies are highly specific for SLE (though not sensitive), targeting snRNP proteins involved in mRNA splicing.

Question 66: Acne vulgaris is primarily caused by which organism?

Staphylococcus aureus
Malassezia furfur
Cutibacterium acnes (Correct answer)
Streptococcus pyogenes

Correct answer: Cutibacterium acnes

Acne vulgaris is primarily caused by Cutibacterium acnes (formerly Propionibacterium acnes), which colonizes hair follicles in sebum-rich areas.

Question 67: Which dermatological condition is characterized by erythematous plaques with silvery scales?

Vitiligo
Rosacea
Eczema
Psoriasis (Correct answer)

Correct answer: Psoriasis

Psoriasis is characterized by well-demarcated erythematous plaques covered with silvery-white scales caused by accelerated keratinocyte turnover.

Question 68: What does 'bilateral' mean?

One side only
Both sides (Correct answer)
The middle
The front

Correct answer: Both sides

Bi- (two) + lateral (side) = pertaining to or affecting both sides.

Question 69: A 52-year-old man presents with a new right bundle branch block and first-degree AV block. He recently returned from camping in Connecticut and has a migratory circular rash. What is the most appropriate treatment?

Azithromycin orally
Doxycycline orally for 14–21 days (Correct answer)
Ciprofloxacin orally
IV ceftriaxone for 14 days

Correct answer: Doxycycline orally for 14–21 days

Early disseminated Lyme disease with cardiac involvement (AV block <second-degree) is treated with oral doxycycline; IV ceftriaxone is reserved for high-degree AV block or other severe manifestations.

Question 70: A 25-year-old man sustains a knee injury while playing soccer. He reports hearing a 'pop' and has a positive anterior drawer test. Which structure is most likely injured?

Anterior cruciate ligament (Correct answer)
Posterior cruciate ligament
Medial collateral ligament
Lateral meniscus

Correct answer: Anterior cruciate ligament

A positive anterior drawer test (anterior tibial translation on the femur) indicates anterior cruciate ligament (ACL) tear.

Question 71: A patient presents with malar rash, joint pain, and positive ANA. The most likely diagnosis is:

Psoriatic arthritis
Lyme disease
Rheumatoid arthritis
Systemic lupus erythematosus (Correct answer)

Correct answer: Systemic lupus erythematosus

The combination of malar (butterfly) rash, arthritis, and positive ANA is classic for systemic lupus erythematosus (SLE).

Question 72: What is the most common cause of primary postpartum hemorrhage (PPH)?

Retained placental fragments
Genital tract lacerations
Uterine atony (Correct answer)
Inherited coagulopathy

Correct answer: Uterine atony

Uterine atony — failure of the uterus to contract after delivery — accounts for approximately 80% of postpartum hemorrhage cases.

Question 73: Which enzyme converts angiotensin I to angiotensin II and is inhibited by ACE inhibitors?

Neprilysin
Aldosterone synthase
Angiotensin-converting enzyme (Correct answer)
Renin

Correct answer: Angiotensin-converting enzyme

ACE (angiotensin-converting enzyme) cleaves angiotensin I to form the vasoactive angiotensin II, and ACE inhibitors block this step.

Question 74: A patient with severe COPD exacerbation is placed on supplemental oxygen. After 30 minutes, he becomes drowsy and his PaCO2 rises from 55 to 75 mmHg. What is the most likely mechanism?

Oxygen-induced cardiac depression
Worsening bronchospasm from oxygen
Loss of hypoxic pulmonary vasoconstriction causing increased V/Q mismatch (Haldane effect) (Correct answer)
Pneumonia worsening secretions

Correct answer: Loss of hypoxic pulmonary vasoconstriction causing increased V/Q mismatch (Haldane effect)

High-flow O2 in chronic CO2 retainers causes the Haldane effect (CO2 displaced from hemoglobin) and worsens V/Q mismatch by reversing hypoxic pulmonary vasoconstriction, raising PaCO2.

Question 75: A 45-year-old man with a history of a recent dental procedure followed by a prolonged course of clindamycin presents with profuse, watery, non-bloody diarrhea and lower abdominal cramping. Stool assay is positive for toxins A and B. What is the primary mechanism of action of these toxins produced by the causative organism?

Inactivation of Rho family GTPases, causing cytoskeletal disruption and epithelial cell death. (Correct answer)
Superantigen activity, leading to widespread T-cell activation and cytokine release.
Inhibition of protein synthesis by blocking the EF-2 translocation step.
Activation of adenylate cyclase, leading to increased intracellular cAMP and massive fluid secretion.

Correct answer: Inactivation of Rho family GTPases, causing cytoskeletal disruption and epithelial cell death.

The patient's presentation is classic for Clostridioides difficile infection (CDI), often precipitated by antibiotics like clindamycin. The primary virulence factors are Toxin A (TcdA) and Toxin B (TcdB), which are glucosyltransferases. They inactivate small GTP-binding proteins of the Rho family within intestinal epithelial cells, leading to actin cytoskeleton disruption, cell rounding, apoptosis, and loss of epithelial barrier function, which results in colitis and diarrhea. [1, 7, 9]

Question 76: A patient with a large left-sided pleural effusion undergoes thoracentesis. After removal of 1.2 L, the patient develops acute chest tightness and CT shows ipsilateral pulmonary infiltrates. What is the most likely complication?

Paradoxical embolism
Re-expansion pulmonary edema (Correct answer)
Hemothorax from intercostal vessel injury
Tension pneumothorax

Correct answer: Re-expansion pulmonary edema

Re-expansion pulmonary edema is a rare but serious complication of rapid large-volume thoracentesis, caused by rapid re-expansion of the collapsed lung.

Question 77: A 65-year-old man presents with a 3-day history of fever, productive cough, and shortness of breath. A chest x-ray confirms a right lower lobe infiltrate. His vitals are: RR 32/min, BP 88/55 mmHg, and he is newly confused. His BUN is 25 mg/dL. Based on the CURB-65 score, what is the most appropriate management setting for this patient with community-acquired pneumonia (CAP)?

Consideration for outpatient management with close follow-up.
Inpatient hospital admission to a general medical ward.
Inpatient hospital admission, likely to the ICU. (Correct answer)
Outpatient management with oral antibiotics.

Correct answer: Inpatient hospital admission, likely to the ICU.

The CURB-65 score helps determine the severity and mortality risk of community-acquired pneumonia. The patient scores 1 point for Confusion, 1 for Urea (>7 mmol/L or ~19.6 mg/dL), 1 for Respiratory rate (≥30/min), and 1 for Blood pressure (systolic <90 or diastolic ≤60). His age (≥65) is not given as a factor in the stem, but even with these 4 points, his score is ≥3. A score of 3 or more indicates high-risk CAP with high mortality, warranting urgent inpatient admission and consideration for ICU level of care.

Question 78: A 55-year-old presents with progressive dyspnea and chest tightness. Spirometry shows FEV1 86% predicted, FVC 87% predicted, FEV1/FVC 0.79. Diffusing capacity (DLCO) is 48% predicted. What diagnosis is most consistent?

Pulmonary vascular disease (Correct answer)
Upper airway obstruction
Mild COPD
Early restrictive lung disease

Correct answer: Pulmonary vascular disease

Isolated severe reduction in DLCO with normal spirometry and FEV1/FVC ratio suggests pulmonary vascular disease (e.g., pulmonary hypertension or pulmonary emboli).

Question 79: According to DSM-5, how many total symptoms (including depressed mood or anhedonia) are required for a diagnosis of Major Depressive Disorder over a minimum 2-week period?

5 (Correct answer)
4
7
3

Correct answer: 5

DSM-5 requires at least 5 of 9 symptoms (including depressed mood or anhedonia as one) present for at least 2 weeks, causing significant functional impairment.

Question 80: A 58-year-old with COPD has an FEV1/FVC ratio of 0.62 and FEV1 of 48% predicted. He remains symptomatic on LABA monotherapy. What is the most appropriate next step?

Add inhaled corticosteroid (ICS)
Add long-acting muscarinic antagonist (LAMA) (Correct answer)
Start oral theophylline
Initiate roflumilast

Correct answer: Add long-acting muscarinic antagonist (LAMA)

GOLD guidelines recommend dual bronchodilation (LABA + LAMA) for COPD patients symptomatic on monotherapy before adding ICS.

Question 81: A mechanically ventilated patient with ARDS has plateau pressure of 34 cmH2O despite tidal volume of 6 mL/kg IBW. Driving pressure is 18 cmH2O. What intervention has been shown to reduce mortality?

High-frequency oscillatory ventilation
Inhaled prostacyclin
Prone positioning for ≥16 hours/day (Correct answer)
Extracorporeal CO2 removal

Correct answer: Prone positioning for ≥16 hours/day

Prone positioning for ≥16 hours/day reduces mortality in moderate-to-severe ARDS (PaO2/FiO2 <150) as demonstrated in the PROSEVA trial.

Question 82: A patient in cardiogenic shock has a pulmonary capillary wedge pressure of 28 mmHg and cardiac index of 1.6 L/min/m². Which pathophysiologic finding best explains the elevated lactate?

Respiratory alkalosis from mechanical ventilation
Inadequate oxygen delivery causing anaerobic metabolism in peripheral tissues (Correct answer)
Hepatic glycogenolysis stimulated by catecholamines
Renal tubular acidosis from diuretic use

Correct answer: Inadequate oxygen delivery causing anaerobic metabolism in peripheral tissues

Low cardiac output in cardiogenic shock results in inadequate systemic oxygen delivery, forcing peripheral tissues to generate ATP anaerobically with lactate as a byproduct.

Question 83: A transplant patient on tacrolimus develops fever and a lung nodule with surrounding halo on CT. Bronchoalveolar lavage shows septate hyphae with acute angle branching (45°). Which antifungal is first-line?

Fluconazole
Caspofungin
Amphotericin B deoxycholate
Voriconazole (Correct answer)

Correct answer: Voriconazole

Invasive pulmonary aspergillosis in immunocompromised patients is caused by Aspergillus species (septate hyphae, 45° branching) and treated first-line with voriconazole.

Question 84: A 25-year-old presents with painless cervical lymphadenopathy and night sweats after a cat scratch. Warthin-Starry silver stain of a lymph node biopsy shows pleomorphic gram-negative rods. Which organism is responsible?

Yersinia pestis
Bartonella henselae (Correct answer)
Pasteurella multocida
Francisella tularensis

Correct answer: Bartonella henselae

Cat-scratch disease is caused by Bartonella henselae, transmitted by cat scratch or bite, producing regional lymphadenopathy; Warthin-Starry silver stain identifies the organisms in tissue.

Question 85: A 50-year-old with a history of hypertension develops sudden onset of rotatory vertigo, nausea, and inability to walk. There is nystagmus and ipsilateral limb ataxia. Which structure is most likely affected?

Brainstem (pons)
Vestibular nerve
Cerebellum (posterior inferior) (Correct answer)
Cochlea

Correct answer: Cerebellum (posterior inferior)

Sudden vertigo with ipsilateral limb ataxia and inability to walk points to cerebellar infarction in the PICA territory, which is a stroke emergency.

Question 86: Renal tubular acidosis type IV is caused by which mechanism?

Hypoaldosteronism impairing K+ and H+ excretion (Correct answer)
Defective proximal HCO3 reabsorption
Defective distal H+ secretion
Carbonic anhydrase deficiency

Correct answer: Hypoaldosteronism impairing K+ and H+ excretion

Type IV RTA results from aldosterone deficiency or resistance, impairing both K+ and H+ secretion in the collecting duct, causing hyperkalemia and a normal anion gap acidosis.

Question 87: A 50-year-old man undergoes total gastrectomy for gastric cancer. Which nutritional deficiency will he inevitably develop without supplementation?

Iron deficiency anemia only
Folate deficiency
Vitamin D deficiency
Vitamin B12 deficiency (Correct answer)

Correct answer: Vitamin B12 deficiency

Total gastrectomy eliminates production of intrinsic factor by parietal cells, making it impossible to absorb vitamin B12 via the ileal receptor, necessitating parenteral supplementation.

Question 88: A diabetic patient develops painful peripheral neuropathy. Tight glycemic control is initiated. Which additional medication has the best evidence for symptomatic relief of diabetic peripheral neuropathy?

NSAIDs
Methotrexate
Hydrocodone alone
Gabapentin or pregabalin (Correct answer)

Correct answer: Gabapentin or pregabalin

Gabapentin and pregabalin are FDA-approved and first-line agents for painful diabetic peripheral neuropathy, modulating calcium channel activity in sensory neurons.

Question 89: A patient with multiple myeloma develops acute kidney injury. Light chain casts in tubules are noted on biopsy. What is this condition called?

Light chain deposition disease
Amyloid nephropathy
Cryoglobulinemic nephritis
Cast nephropathy (myeloma kidney) (Correct answer)

Correct answer: Cast nephropathy (myeloma kidney)

Cast nephropathy (myeloma kidney) occurs when monoclonal light chains precipitate with Tamm-Horsfall protein in tubules, causing obstruction and AKI.

Question 90: A 50-year-old presents with rapidly progressive dementia, myoclonus, and periodic sharp wave complexes on EEG. CSF 14-3-3 protein is elevated. MRI shows cortical ribboning on DWI. What is the diagnosis?

Anti-NMDA receptor encephalitis
Hashimoto encephalopathy
Viral encephalitis
Creutzfeldt-Jakob disease (Correct answer)

Correct answer: Creutzfeldt-Jakob disease

Rapidly progressive dementia with myoclonus, periodic EEG complexes, CSF 14-3-3, and DWI cortical ribboning is classic for Creutzfeldt-Jakob disease.

Question 91: A 40-year-old male nonsmoker presents with lower lobe-predominant emphysema detected on CT. Serum AAT level is 45 mg/dL (normal >100). What is the most appropriate specific treatment?

Lung volume reduction surgery
Intravenous alpha-1 antitrypsin augmentation therapy (Correct answer)
High-dose vitamin E supplementation
Prophylactic azithromycin

Correct answer: Intravenous alpha-1 antitrypsin augmentation therapy

IV AAT augmentation therapy is specifically indicated for patients with severe alpha-1 antitrypsin deficiency (Pi*ZZ genotype) and established airflow obstruction.

Question 92: A 25-year-old woman has muscle cramps, perioral tingling, and a positive Chvostek sign after thyroid surgery. Labs show calcium 7.0 mg/dL and PTH 5 pg/mL. What is the diagnosis?

Pseudohypoparathyroidism
Hypomagnesemia
Vitamin D deficiency
Hypoparathyroidism (Correct answer)

Correct answer: Hypoparathyroidism

Surgical removal or damage to parathyroid glands causes hypoparathyroidism with low calcium and very low PTH.

Question 93: A 6-year-old develops red strawberry tongue, scarlatiniform rash, and perioral pallor. Throat swab grows beta-hemolytic group A streptococcus. Which complication can be prevented by treating with penicillin?

Rheumatic fever (Correct answer)
Toxic shock syndrome
Post-streptococcal glomerulonephritis
Peritonsillar abscess

Correct answer: Rheumatic fever

Antibiotic treatment of group A streptococcal pharyngitis prevents acute rheumatic fever (but NOT post-streptococcal glomerulonephritis, which is not prevented by antibiotics).

Question 94: A 55-year-old woman has hypercalcemia, nephrolithiasis, and a serum PTH of 95 pg/mL (normal 10–65). Which parathyroid disorder is most consistent?

Secondary hyperparathyroidism
Primary hyperparathyroidism (Correct answer)
Hypoparathyroidism
Pseudohypoparathyroidism

Correct answer: Primary hyperparathyroidism

Primary hyperparathyroidism causes hypercalcemia with inappropriately elevated PTH, typically due to a parathyroid adenoma.

Question 95: A 28-year-old man presents with profuse watery diarrhea (rice-water stools) after returning from Southeast Asia. He is severely dehydrated. What organism is most likely responsible?

Shigella dysenteriae
Giardia lamblia
Salmonella typhi
Vibrio cholerae (Correct answer)

Correct answer: Vibrio cholerae

Vibrio cholerae produces cholera toxin that causes ADP-ribosylation of Gs protein, leading to massive secretory diarrhea with characteristic rice-water appearance.

Question 96: A 45-year-old woman presents with weight gain, fatigue, and constipation. Labs show TSH 12 mIU/L and free T4 0.6 ng/dL. Which finding would most likely also be present?

Elevated free T3
Hypercalcemia
Hypokalemia
Elevated LDL cholesterol (Correct answer)

Correct answer: Elevated LDL cholesterol

Hypothyroidism impairs LDL receptor expression, leading to elevated LDL cholesterol and dyslipidemia.

Question 97: A 50-year-old man has an incidentally found 2.5 cm adrenal mass. Workup shows normal cortisol, normal metanephrines, and normal aldosterone/renin ratio. What is the recommended management?

Start empiric ketoconazole
Fine-needle aspiration biopsy
Repeat imaging in 6–12 months (Correct answer)
Immediate surgical resection

Correct answer: Repeat imaging in 6–12 months

A hormonally inactive adrenal incidentaloma <4 cm with benign imaging features should be monitored with repeat imaging at 6–12 months.

Question 98: A 45-year-old with AIDS (CD4 60 cells/μL) develops progressive bilateral visual loss described as 'pizza pie' fundus with perivascular hemorrhages and exudates. Which organism is responsible?

Pneumocystis jirovecii
Herpes simplex virus-1
Toxoplasma gondii
Cytomegalovirus (Correct answer)

Correct answer: Cytomegalovirus

CMV retinitis is the most common ocular opportunistic infection in AIDS patients with CD4 <50, producing the classic 'pizza pie' or 'scrambled eggs' appearance with hemorrhagic necrosis on funduscopy.

Question 99: A patient with Graves' disease is started on methimazole. Which of the following best describes the primary mechanism of action of this thionamide medication?

It competitively blocks the TSH receptor on thyroid follicular cells.
It blocks the peripheral conversion of T4 to T3.
It inhibits the thyroid peroxidase enzyme, blocking the organification of iodine. (Correct answer)
It destroys thyroid follicular cells through radioactive emission.

Correct answer: It inhibits the thyroid peroxidase enzyme, blocking the organification of iodine.

Methimazole's primary mechanism of action is the inhibition of the thyroid peroxidase (TPO) enzyme. This enzyme is crucial for oxidizing iodide and coupling it to tyrosine residues on thyroglobulin (a process called organification), which is a critical step in the synthesis of thyroid hormones T3 and T4. Propylthiouracil (PTU) also inhibits TPO but has the additional effect of blocking the peripheral conversion of T4 to T3.

Question 100: A patient's labs show: glucose 90 mg/dL, sodium 130 mEq/L, potassium 5.8 mEq/L, bicarbonate 14 mEq/L, and a morning cortisol of 2 mcg/dL. ACTH stimulation test shows a blunted response. Which diagnosis fits?

Primary adrenal insufficiency (Addison's disease) (Correct answer)
Secondary adrenal insufficiency
Cushing's disease
Conn's syndrome

Correct answer: Primary adrenal insufficiency (Addison's disease)

Primary adrenal insufficiency features hyperkalemia (from mineralocorticoid deficiency), hyponatremia, and a blunted cortisol response to ACTH stimulation.

Question 101: A 75-year-old woman was recently diagnosed with polymyalgia rheumatica (PMR). During a follow-up visit, she reports developing a new, unilateral headache over her right temple and jaw claudication when chewing. Which of the following conditions is most likely associated with her PMR and new symptoms?

Trigeminal neuralgia
Cervical spondylosis
Fibromyalgia
Giant Cell Arteritis (GCA) (Correct answer)

Correct answer: Giant Cell Arteritis (GCA)

Polymyalgia rheumatica and Giant Cell Arteritis are closely related inflammatory conditions. Approximately 50% of patients with GCA also have PMR, and about 15-20% of patients with PMR will develop GCA. The new onset of headache, jaw claudication, and temporal tenderness in an elderly patient with PMR is highly suspicious for GCA, a vasculitis that can lead to irreversible blindness if not promptly treated with high-dose corticosteroids.

Question 102: A patient with renal cell carcinoma has polycythemia. What is the mechanism?

Dehydration causing hemoconcentration
Paraneoplastic PTHrP secretion
Tumor secretion of EPO leading to increased RBC production (Correct answer)
Iron deficiency causing compensatory erythropoiesis

Correct answer: Tumor secretion of EPO leading to increased RBC production

RCC can autonomously secrete erythropoietin as a paraneoplastic syndrome, stimulating erythropoiesis and causing polycythemia.

Question 103: Podocyte injury leading to foot process effacement is the hallmark of which glomerular disease?

Focal segmental glomerulosclerosis
Membranous nephropathy
Minimal change disease (Correct answer)
IgA nephropathy

Correct answer: Minimal change disease

Minimal change disease shows diffuse podocyte foot process effacement on electron microscopy with no changes on light microscopy.

Question 104: A 70-year-old presents with progressive gait instability, urinary incontinence, and cognitive decline. MRI shows enlarged ventricles disproportionate to sulcal atrophy. What is the diagnosis?

Vascular dementia
Alzheimer dementia
Lewy body dementia
Normal pressure hydrocephalus (Correct answer)

Correct answer: Normal pressure hydrocephalus

The classic triad of gait apraxia, urinary incontinence, and dementia with ventriculomegaly suggests normal pressure hydrocephalus.

Question 105: In the setting of acute myocardial infarction, early reperfusion can paradoxically cause cell death through which mechanism?

Reperfusion injury from calcium overload, reactive oxygen species, and mitochondrial permeability transition pore opening (Correct answer)
Hyperemia causing mechanical rupture of infarcted myocytes
Re-entry arrhythmias from restored conduction
Sudden normalization of pH inactivating contractile proteins

Correct answer: Reperfusion injury from calcium overload, reactive oxygen species, and mitochondrial permeability transition pore opening

Restored blood flow delivers oxygen to cells with depleted antioxidant defenses, generating ROS that open the mitochondrial permeability transition pore, leading to additional cardiomyocyte death.

Question 106: A 30-year-old woman with SLE develops new hematuria and proteinuria. Renal biopsy shows diffuse proliferative glomerulonephritis with 'wire-loop' lesions. What class of lupus nephritis is this?

Class III (focal lupus nephritis)
Class II (mesangial proliferative)
Class V (membranous lupus nephritis)
Class IV (diffuse lupus nephritis) (Correct answer)

Correct answer: Class IV (diffuse lupus nephritis)

Class IV diffuse lupus nephritis is the most severe form, characterized by diffuse glomerular involvement and wire-loop lesions from subendothelial immune complex deposits.

Question 107: A patient with NHL undergoing CHOP chemotherapy develops neutropenic fever on day 10. ANC is 200/μL. What is the most appropriate initial empiric antibiotic choice?

Vancomycin + metronidazole
Caspofungin alone
Oral ciprofloxacin monotherapy
Antipseudomonal beta-lactam (e.g., piperacillin-tazobactam) (Correct answer)

Correct answer: Antipseudomonal beta-lactam (e.g., piperacillin-tazobactam)

IDSA guidelines recommend empiric broad-spectrum antipseudomonal beta-lactam monotherapy as initial treatment for febrile neutropenia.

Question 108: The combining form 'pneumo-' or 'pneumono-' refers to:

Lung (Correct answer)
Kidney
Bladder
Liver

Correct answer: Lung

Pneumo- derives from Greek 'pneumon' meaning lung or air.

Question 109: A patient with newly diagnosed hypothyroidism is started on levothyroxine. When should TSH be rechecked to assess adequacy of dosing?

Only when symptoms recur
After 1 week
After 4–6 weeks (Correct answer)
After 6 months

Correct answer: After 4–6 weeks

TSH has a half-life that requires 4–6 weeks for a new steady state to be reached after initiating or adjusting levothyroxine therapy.

Question 110: A 25-year-old sexually active woman has a painless genital ulcer with a raised, indurated edge and non-tender inguinal lymphadenopathy. Dark-field microscopy shows motile spirochetes. Which stage of syphilis is this?

Primary syphilis (Correct answer)
Tertiary (late) syphilis
Latent syphilis
Secondary syphilis

Correct answer: Primary syphilis

Primary syphilis presents as a single painless, indurated chancre at the inoculation site with regional lymphadenopathy, caused by Treponema pallidum visible on dark-field microscopy.

Question 111: Seborrheic dermatitis preferentially affects which body regions?

Lower extremities and dorsal feet
Palms and soles
Elbows, knees, and sacrum
Scalp, face, and anterior chest (Correct answer)

Correct answer: Scalp, face, and anterior chest

Seborrheic dermatitis primarily affects sebaceous gland-rich areas including the scalp, nasolabial folds, eyebrows, and anterior chest.

Question 112: A 45-year-old presents with fatigue, splenomegaly, and a WBC of 120,000/μL with a left shift. Cytogenetics reveals t(9;22). Which kinase is constitutively activated in this condition?

JAK2
FLT3
BCR-ABL1 (Correct answer)
KIT

Correct answer: BCR-ABL1

The Philadelphia chromosome t(9;22) creates the BCR-ABL1 fusion gene, producing a constitutively active tyrosine kinase that drives CML.

Question 113: A 52-year-old male is diagnosed with a duodenal ulcer, and a urease breath test is positive for Helicobacter pylori. He has no known drug allergies. According to the most recent ACG (American College of Gastroenterology) guidelines, which of the following is a recommended first-line treatment regimen?

Esomeprazole and ranitidine for 8 weeks.
Bismuth subsalicylate, metronidazole, tetracycline, and a PPI for 14 days. (Correct answer)
A proton pump inhibitor (PPI) and amoxicillin for 10 days.
Omeprazole, clarithromycin, and metronidazole for 7 days.

Correct answer: Bismuth subsalicylate, metronidazole, tetracycline, and a PPI for 14 days.

Recent ACG guidelines recommend bismuth quadruple therapy (a PPI, bismuth, metronidazole, and tetracycline for 14 days) as a preferred first-line treatment for H. pylori, largely due to rising clarithromycin resistance. Clarithromycin-based triple therapy is no longer recommended as a primary empiric option in many regions. A PPI and amoxicillin alone is insufficient for eradication. A PPI with an H2 blocker will heal the ulcer but not treat the underlying H. pylori infection.

Question 114: A 62-year-old man with type 2 diabetes has an eGFR of 35 mL/min/1.73m². Which glucose-lowering agent should be AVOIDED due to risk of lactic acidosis?

Empagliflozin
Metformin (Correct answer)
Insulin glargine
Sitagliptin

Correct answer: Metformin

Metformin is contraindicated when eGFR falls below 30 and requires dose reduction below 45 due to accumulation and risk of lactic acidosis.

Question 115: A 28-year-old woman returns from Southeast Asia with cyclic fevers every 72 hours, severe anemia, and splenomegaly. Peripheral blood smear shows ring forms and banana-shaped gametocytes. Which Plasmodium species is most likely?

P. malariae
P. vivax
P. ovale
P. falciparum (Correct answer)

Correct answer: P. falciparum

P. falciparum causes 48-hour (tertian) fevers and is the only species producing banana-shaped (crescent) gametocytes; it causes the most severe malaria with high parasitemia.

Question 116: A 28-year-old presents with subacute confusion, psychiatric symptoms, orofacial dyskinesias, and CSF showing mild pleocytosis. What is the most likely diagnosis?

Syphilitic meningitis
Anti-NMDA receptor encephalitis (Correct answer)
Tuberculous meningitis
Herpes simplex encephalitis

Correct answer: Anti-NMDA receptor encephalitis

Anti-NMDA receptor encephalitis classically presents in young women with psychiatric prodrome, dyskinesias, autonomic instability, and CSF pleocytosis.

Question 117: A 40-year-old man with recurrent kidney stones is found to have hypercalcemia and nephrolithiasis. He also complains of abdominal pain and peptic ulcers. What syndrome should be suspected?

VIPoma
Zollinger-Ellison syndrome
Carcinoid syndrome
Multiple Endocrine Neoplasia type 1 (MEN1) (Correct answer)

Correct answer: Multiple Endocrine Neoplasia type 1 (MEN1)

MEN1 (Wermer syndrome) involves tumors of the parathyroids, pancreatic islets (including gastrinomas causing peptic ulcers), and pituitary gland.

Question 118: Which diuretic acts on the thick ascending limb of the loop of Henle and is most effective in patients with reduced GFR?

Amiloride
Hydrochlorothiazide
Spironolactone
Furosemide (Correct answer)

Correct answer: Furosemide

Furosemide (a loop diuretic) inhibits the Na-K-2Cl cotransporter in the thick ascending limb and remains effective even with low GFR, unlike thiazides.

Question 119: A 72-year-old male with end-stage renal disease presents to the ER with severe weakness and palpitations. An ECG shows peaked T waves and a widened QRS complex. His serum potassium is 7.2 mEq/L. What is the most appropriate initial step in management to stabilize the cardiac membrane?

Administer intravenous calcium gluconate. (Correct answer)
Arrange for emergent hemodialysis.
Administer intravenous regular insulin and glucose.
Administer intravenous sodium bicarbonate.

Correct answer: Administer intravenous calcium gluconate.

In a patient with severe hyperkalemia and ECG changes, the immediate priority is to stabilize the cardiac membrane to prevent life-threatening arrhythmias. Intravenous calcium gluconate (or calcium chloride) directly antagonizes the membrane-depolarizing effects of hyperkalemia without lowering the serum potassium level. While insulin/glucose, sodium bicarbonate, and hemodialysis are all crucial for lowering total body potassium, they act more slowly and do not provide immediate cardioprotection.

Question 120: Which gene mutation, found in >95% of polycythemia vera patients, is used as a diagnostic criterion?

MPL W515
JAK2 V617F (Correct answer)
BCR-ABL1
CALR exon 9

Correct answer: JAK2 V617F

JAK2 V617F is present in >95% of PV patients and causes constitutive JAK-STAT signaling, driving erythrocytosis independent of EPO.

Question 121: First-line treatment for PCOS with irregular menses when pregnancy is NOT desired is:

Clomiphene citrate
Gonadotropin injections
Metformin alone
Combined oral contraceptive pills (Correct answer)

Correct answer: Combined oral contraceptive pills

Combined oral contraceptives are first-line therapy for menstrual irregularity in PCOS, reducing LH-driven androgen production and regulating cycle length.

Question 122: The standard US screening approach for gestational diabetes at 24-28 weeks gestation is:

Fasting plasma glucose alone
Random plasma glucose
HbA1c measurement
Two-step: 50g GCT then 100g OGTT if abnormal (Correct answer)

Correct answer: Two-step: 50g GCT then 100g OGTT if abnormal

The two-step approach — a 1-hour 50g glucose challenge test followed by a 3-hour 100g OGTT if the screen is positive — is the standard US method for GDM screening.

Question 123: Which ultraviolet radiation type is most strongly associated with melanoma development?

Infrared radiation
UVA (320-400 nm) (Correct answer)
UVC (100-290 nm)
UVB (290-320 nm)

Correct answer: UVA (320-400 nm)

UVA radiation penetrates deeply into the dermis and is primarily associated with melanoma through indirect oxidative DNA damage.

Question 124: A patient with cervical myelopathy presents with bilateral upper extremity weakness, hand clumsiness, and hyperreflexia in the legs. What is the most appropriate initial imaging?

CT myelography
MRI cervical spine without contrast (Correct answer)
EMG/nerve conduction study
Plain cervical X-ray

Correct answer: MRI cervical spine without contrast

MRI of the cervical spine is the first-line imaging for suspected myelopathy, best demonstrating cord compression and signal changes.

Question 125: A patient with ulcerative colitis limited to the rectum is best described as having which subtype?

Pancolitis
Ileocolitis
Left-sided colitis
Proctitis (Correct answer)

Correct answer: Proctitis

Proctitis refers to ulcerative colitis confined to the rectum, the most distal and mildest form of the disease.

Question 126: An HIV-positive patient with CD4 count of 150 cells/μL develops ring-enhancing brain lesions on MRI with surrounding edema. Serology is positive for IgG antibodies. What is the most likely diagnosis and empiric treatment?

Cryptococcal meningitis; fluconazole
Cerebral toxoplasmosis; pyrimethamine + sulfadiazine (Correct answer)
CNS lymphoma; methotrexate
Progressive multifocal leukoencephalopathy; antiretrovirals

Correct answer: Cerebral toxoplasmosis; pyrimethamine + sulfadiazine

Multiple ring-enhancing lesions in an HIV patient with positive Toxoplasma IgG should be treated empirically with pyrimethamine + sulfadiazine (+ leucovorin); response within 2 weeks confirms diagnosis.

Question 127: A 45-year-old with history of alcohol abuse presents with confusion, ophthalmoplegia, and ataxia. What should be administered immediately?

Naloxone IV
Glucose bolus
Lorazepam IV
Thiamine IV before glucose (Correct answer)

Correct answer: Thiamine IV before glucose

Thiamine must be given before glucose to prevent precipitating Wernicke encephalopathy in thiamine-deficient patients.

Question 128: A 55-year-old woman is newly diagnosed with Pulmonary Arterial Hypertension (PAH), classified as low-to-intermediate risk. She has no significant comorbidities. According to current treatment guidelines, what is the recommended initial therapeutic strategy?

Monotherapy with an endothelin receptor antagonist (ERA).
Initial combination therapy with an ERA and a PDE-5 inhibitor. (Correct answer)
Immediate referral for lung transplantation evaluation.
Monotherapy with a calcium channel blocker.

Correct answer: Initial combination therapy with an ERA and a PDE-5 inhibitor.

Current guidelines from bodies like the ESC/ERS recommend initial oral combination therapy for most newly diagnosed PAH patients who are not at high risk. The most common initial combination is an endothelin receptor antagonist (ERA) and a phosphodiesterase-5 (PDE-5) inhibitor. Monotherapy is generally reserved for specific situations, and calcium channel blocker monotherapy is only appropriate for the small subset of patients who show a positive response to acute vasoreactivity testing. Immediate transplant referral is reserved for high-risk patients.

Question 129: Which segment of the nephron is impermeable to water under all conditions, even in the presence of ADH?

Collecting duct
Descending limb of loop of Henle
Proximal convoluted tubule
Thick ascending limb of loop of Henle (Correct answer)

Correct answer: Thick ascending limb of loop of Henle

The thick ascending limb is constitutively impermeable to water, allowing it to dilute tubular fluid regardless of ADH levels.

Question 130: Which of the following is considered the first-line and most effective treatment for most patients with moderate to severe obstructive sleep apnea (OSA)?

Weight loss and positional therapy
Mandibular advancement device
Uvulopalatopharyngoplasty (UPPP)
Continuous Positive Airway Pressure (CPAP) (Correct answer)

Correct answer: Continuous Positive Airway Pressure (CPAP)

Continuous Positive Airway Pressure (CPAP) therapy is the gold standard and most effective first-line treatment for moderate to severe obstructive sleep apnea. It works by providing a continuous stream of air to keep the airway open during sleep. While mandibular advancement devices, surgery, and lifestyle modifications like weight loss are also treatment options, they are typically considered for mild to moderate OSA or for patients who cannot tolerate CPAP.

Question 131: A 35-year-old woman with sickle cell disease develops sudden chest pain, fever, hypoxia, and a new pulmonary infiltrate during a painful crisis. The most likely diagnosis is:

Pulmonary embolism
Pulmonary hypertension
Lobar pneumonia
Acute chest syndrome (Correct answer)

Correct answer: Acute chest syndrome

Acute chest syndrome (new pulmonary infiltrate + chest symptoms) is the leading cause of death in sickle cell disease and requires exchange transfusion in severe cases.

Question 132: Which topical agent is considered first-line for mild-to-moderate acne vulgaris?

Benzoyl peroxide (Correct answer)
Triamcinolone
Isotretinoin
Oral tetracycline

Correct answer: Benzoyl peroxide

Benzoyl peroxide is first-line topical treatment for mild-to-moderate acne due to its antibacterial, keratolytic, and comedolytic properties.

Question 133: A 55-year-old with scleroderma develops progressive exertional dyspnea. Echocardiogram shows RVSP of 55 mmHg. Right heart catheterization confirms mPAP of 38 mmHg with normal PCWP. What is the most appropriate initial therapy?

Subcutaneous treprostinil
Oral sildenafil (Correct answer)
Oral bosentan
Intravenous epoprostenol

Correct answer: Oral sildenafil

For WHO functional class II-III pulmonary arterial hypertension, oral PDE-5 inhibitors like sildenafil or ERA like ambrisentan/bosentan are recommended initial therapy.

Question 134: Which suffix means 'surgical creation of an opening'?

-ostomy (Correct answer)
-otomy
-plasty
-ectomy

Correct answer: -ostomy

-Ostomy means surgical creation of a permanent or semi-permanent opening.

Question 135: A 22-year-old college student presents with fever, severe headache, photophobia, and neck stiffness. CSF shows WBC 2,000 (90% PMNs), low glucose, high protein. What is empiric treatment?

Amphotericin B
Acyclovir alone
Ceftriaxone + vancomycin + dexamethasone (Correct answer)
Doxycycline

Correct answer: Ceftriaxone + vancomycin + dexamethasone

Bacterial meningitis is treated empirically with ceftriaxone plus vancomycin (for resistant pneumococcus) and dexamethasone to reduce inflammation.

Question 136: A 50-year-old woman with rheumatoid arthritis develops atlantoaxial instability. Which cervical vertebrae are involved, and what is the primary danger?

C1-C2 instability with risk of spinal cord compression (Correct answer)
C3-C4 instability with diaphragm paralysis
C2-C3 instability with vertebral artery injury
C5-C6 instability with nerve root compression

Correct answer: C1-C2 instability with risk of spinal cord compression

RA-related erosion of the transverse ligament causes C1-C2 (atlantoaxial) instability, risking odontoid process compression of the spinal cord.

Question 137: With complaints of restlessness, agitation, palpitations, sweating, and considerable weight loss of 8 pounds (without any food or exercise intervention), a 34-year-old woman who is a mother of three visits her general care physician. She also complains of fine trembling and heat sensitivity. She vehemently denies using any form of tobacco, alcohol, or caffeine. Her vital signs are as follows: 37 C (98.6 F), 120 beats per minute for her heartbeat, 140/80 mmHg for her blood pressure, and 20 beats per minute for her breathing. During a physical examination, the doctor noted a pre-tibial myxedema, lid lag, and distinctive gaze in addition to a fine tremor. The thyroid gland is lobular and diffusely enlarged upon palpation. On auscultation, a bruit is audible over the surface of the gland. TSH levels are extremely low, and radioactive iodine uptake is boosted, according to lab tests. Graves disease is identified, and potential therapies are addressed. What long-term risks are there if the patient chooses radioactive iodine therapy?

Hypothyroidism (Correct answer)
Cholestasis
Recurrent laryngeal nerve damage
Carcinoma of thyroid gland

Correct answer: Hypothyroidism

Radioactive iodine therapy (RAI) for Graves' disease works by destroying overactive thyroid cells, reducing the production of thyroid hormones. A common long-term consequence is that too much thyroid tissue is destroyed, leading to insufficient hormone production. This results in iatrogenic hypothyroidism, which then requires lifelong thyroid hormone replacement therapy.

Question 138: A 40-year-old woman has a TSH of 0.05 mIU/L and elevated free T4. She reports palpitations, heat intolerance, and a diffuse goiter with bruit on exam. What autoantibody confirms the diagnosis?

Anti-thyroglobulin
TSH receptor antibody (TRAb) (Correct answer)
Anti-thyroid peroxidase (anti-TPO)
Anti-microsomal antibody

Correct answer: TSH receptor antibody (TRAb)

TSH receptor-stimulating antibodies (TRAb) are pathognomonic for Graves' disease, causing diffuse goiter and hyperthyroidism.

Question 139: A 75-year-old man is brought to the emergency department 90 minutes after the sudden onset of left-sided weakness and facial droop. A non-contrast head CT scan shows no evidence of intracranial hemorrhage. His blood pressure is 170/95 mmHg. What is the most appropriate immediate intervention?

Observation and supportive care with repeat CT in 24 hours
Administration of intravenous alteplase (tPA) (Correct answer)
Urgent neurosurgical consultation for hematoma evacuation
Immediate administration of high-dose aspirin

Correct answer: Administration of intravenous alteplase (tPA)

For patients with an acute ischemic stroke who present within the 3 to 4.5-hour therapeutic window and have no contraindications (like hemorrhage on CT), intravenous alteplase (a thrombolytic agent) is the standard of care to restore cerebral blood flow and improve functional outcomes. Aspirin is typically started 24 hours after tPA administration. Neurosurgical consultation would be for a hemorrhagic stroke, not an ischemic one without hemorrhage. Observation alone would miss the critical opportunity for reperfusion therapy.

Question 140: The ABCDE criteria for melanoma screening stands for:

Asymmetry, Border, Color, Diameter, Evolution (Correct answer)
Area, Border, Circumference, Depth, Erythema
Asymmetry, Blistering, Cells, Dermis, Elevation
Age, Bleeding, Color, Diameter, Evolution

Correct answer: Asymmetry, Border, Color, Diameter, Evolution

ABCDE stands for Asymmetry, Border irregularity, Color variation, Diameter greater than 6 mm, and Evolution of the lesion.

Question 141: What is the most common gynecologic malignancy in the United States?

Vulvar cancer
Cervical cancer
Ovarian cancer
Endometrial (uterine) cancer (Correct answer)

Correct answer: Endometrial (uterine) cancer

Endometrial cancer is the most common gynecologic malignancy in the US, typically presenting with postmenopausal uterine bleeding.

Question 142: Placenta previa (placenta overlying the internal os) is best diagnosed by:

Transabdominal ultrasound
Transvaginal ultrasound (Correct answer)
Pelvic MRI
Digital cervical examination

Correct answer: Transvaginal ultrasound

Transvaginal ultrasound is the gold standard for diagnosing placenta previa, providing accurate measurement of the placental edge-to-internal os distance.

Question 143: A patient with long-standing Crohn's disease develops a fistula between the small bowel and bladder (enterovesical fistula). Which symptom would most specifically suggest this complication?

Urinary frequency and urgency
Recurrent urinary tract infections with polymicrobial bacteria (Correct answer)
Dysuria without infection
Hematuria

Correct answer: Recurrent urinary tract infections with polymicrobial bacteria

Enterovesical fistula allows intestinal bacteria to enter the bladder, causing recurrent polymicrobial urinary tract infections and pneumaturia (air in the urine).

Question 144: A 45-year-old man has recurrent calcium oxalate kidney stones. Urinalysis shows hypercalciuria with normal serum calcium. Which dietary modification is most appropriate?

Increase oxalate-rich foods
Increase dietary calcium intake (Correct answer)
Decrease fluid intake
Restrict dietary calcium severely

Correct answer: Increase dietary calcium intake

Adequate dietary calcium binds oxalate in the gut, reducing intestinal oxalate absorption and urinary oxalate excretion.

Question 145: A 45-year-old female presents to the emergency department with a severe asthma exacerbation, refractory to initial treatment with nebulized albuterol/ipratropium and systemic corticosteroids. She is tachypneic and speaking in single words. Which of the following intravenous medications is most appropriate to administer as an adjunctive therapy in this situation?

Magnesium sulfate (Correct answer)
Furosemide
Sodium bicarbonate
Aminophylline

Correct answer: Magnesium sulfate

For severe asthma exacerbations not responding to initial standard therapies (SABAs, anticholinergics, and systemic corticosteroids), intravenous magnesium sulfate is recommended as an adjunctive treatment. It has bronchodilatory properties and can improve lung function and reduce hospitalization rates in severe cases. Furosemide is a diuretic, aminophylline is rarely used due to its narrow therapeutic index and significant side effects, and sodium bicarbonate is not indicated for asthma.

Question 146: A 60-year-old woman develops proximal muscle weakness, elevated CK, and an EMG showing myopathic changes. Muscle biopsy reveals perifascicular atrophy. What is the diagnosis?

Dermatomyositis (Correct answer)
Polymyositis
Inclusion body myositis
Muscular dystrophy

Correct answer: Dermatomyositis

Perifascicular atrophy is pathognomonic for dermatomyositis, reflecting ischemia from complement-mediated microangiopathy of muscle capillaries.

Question 147: A patient with celiac disease continues to have diarrhea despite strict gluten avoidance. Repeat small bowel biopsy shows persistent villous atrophy. What complication should be most urgently considered?

Enteropathy-associated T-cell lymphoma (Correct answer)
Pernicious anemia
Irritable bowel syndrome superimposition
Microscopic colitis

Correct answer: Enteropathy-associated T-cell lymphoma

Refractory celiac disease that does not respond to a gluten-free diet raises concern for enteropathy-associated T-cell lymphoma, a serious malignant complication.

Question 148: A 34-year-old woman presents with chronic diarrhea, bloating, and significant weight loss. Serological testing is positive for IgA anti-tissue transglutaminase (tTG) antibodies. An upper endoscopy with duodenal biopsy is performed. Which of the following biopsy findings would confirm the diagnosis of celiac disease?

Glandular atrophy and intestinal metaplasia
Foamy macrophages within the lamina propria
Villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes (Correct answer)
Transmural inflammation with skip lesions

Correct answer: Villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes

The classic histopathological triad for celiac disease on a duodenal biopsy is villous atrophy, crypt hyperplasia, and an increase in intraepithelial lymphocytes. This combination confirms the diagnosis in the setting of positive serology. Glandular atrophy and intestinal metaplasia are seen in conditions like atrophic gastritis. Foamy macrophages are characteristic of Whipple disease. Transmural inflammation with skip lesions is a feature of Crohn's disease.

Question 149: Which hormone directly stimulates the principal cells of the collecting duct to insert aquaporin-2 channels into the apical membrane?

Aldosterone
Parathyroid hormone
Antidiuretic hormone (ADH) (Correct answer)
Atrial natriuretic peptide

Correct answer: Antidiuretic hormone (ADH)

ADH (vasopressin) binds V2 receptors on principal cells, triggering cAMP-mediated insertion of aquaporin-2 into the apical membrane to increase water permeability.

Question 150: Pelvic inflammatory disease (PID) is most commonly caused by:

Escherichia coli
Staphylococcus aureus
Group B Streptococcus
Neisseria gonorrhoeae and Chlamydia trachomatis (Correct answer)

Correct answer: Neisseria gonorrhoeae and Chlamydia trachomatis

PID is most commonly polymicrobial but predominantly initiated by sexually transmitted organisms — Neisseria gonorrhoeae and Chlamydia trachomatis.

Question 151: Which electrolyte abnormality is most commonly associated with prolonged QT interval and increased risk of torsades de pointes?

Hypernatremia
Hypomagnesemia (Correct answer)
Hyperkalemia
Hyperchloremia

Correct answer: Hypomagnesemia

Hypomagnesemia prolongs the QT interval and is the most common electrolyte cause of torsades de pointes, often treated with IV magnesium sulfate.

Question 152: Free water clearance (CH2O) is negative in a patient. What does this indicate?

Patient's GFR is below normal
Patient has diabetes insipidus
Patient is excreting dilute urine relative to plasma
Patient is excreting concentrated urine and retaining free water (Correct answer)

Correct answer: Patient is excreting concentrated urine and retaining free water

Negative free water clearance means the kidney is excreting urine more concentrated than plasma, retaining free water (as in SIADH or normal ADH response to dehydration).

Question 153: A 45-year-old man with a history of alcohol abuse is brought to the emergency department. He has been continuously seizing for 10 minutes despite pre-hospital administration of an IM benzodiazepine. In the ED, he remains unresponsive and continues to have generalized tonic-clonic seizure activity. After securing the airway and obtaining IV access, which medication should be administered first?

An intravenous bolus of propofol
An intravenous bolus of lorazepam (Correct answer)
A loading dose of oral phenytoin
An intravenous infusion of phenobarbital

Correct answer: An intravenous bolus of lorazepam

The first-line emergent treatment for status epilepticus is an intravenous benzodiazepine. Lorazepam is often preferred due to its rapid onset and relatively longer duration of action compared to diazepam. If seizure activity continues after adequate benzodiazepine administration, a second-line agent like fosphenytoin, levetiracetam, or valproic acid would be used. Propofol and phenobarbital are generally reserved for refractory status epilepticus that has not responded to first and second-line agents. Oral medications are not appropriate for emergent management.

Question 154: A 2-year-old child has multiple fractures, blue sclerae, dentinogenesis imperfecta, and hearing loss. What is the underlying molecular defect?

Mutation in FGFR3 causing abnormal bone growth
Deficiency of vitamin D 1-alpha hydroxylase
Deficiency of alkaline phosphatase
Mutation in COL1A1 or COL1A2 causing defective type I collagen (Correct answer)

Correct answer: Mutation in COL1A1 or COL1A2 causing defective type I collagen

Osteogenesis imperfecta results from mutations in type I collagen genes (COL1A1/COL1A2), producing structurally abnormal collagen that weakens bone, sclerae, and teeth.

Question 155: A 45-year-old man presents with sudden onset of thunderclap headache reaching maximal intensity within seconds. CT head is negative. What is the next best step?

Discharge with analgesics
Start sumatriptan
MRI brain with contrast
Lumbar puncture for xanthochromia (Correct answer)

Correct answer: Lumbar puncture for xanthochromia

A negative CT with thunderclap headache requires lumbar puncture to detect xanthochromia, indicating subarachnoid hemorrhage.

Question 156: A 32-year-old woman with type 1 diabetes presents with recurrent hypoglycemia unawareness. Which physiologic response is impaired?

Increased insulin secretion to compensate
Decreased cortisol release
Increased renal glucose reabsorption
Increased glucagon secretion from alpha cells (Correct answer)

Correct answer: Increased glucagon secretion from alpha cells

Longstanding type 1 diabetes impairs glucagon counterregulatory response to hypoglycemia, removing a critical defense mechanism against low blood sugar.

Question 157: An infant develops profuse watery diarrhea after rotavirus infection. The rotavirus enterotoxin NSP4 primarily causes diarrhea by which mechanism?

Disrupting intestinal epithelial tight junctions via Ca2+ signaling (Correct answer)
Blocking Na+/K+ ATPase
Activating guanylyl cyclase
Inhibiting adenylyl cyclase

Correct answer: Disrupting intestinal epithelial tight junctions via Ca2+ signaling

Rotavirus NSP4 acts as a viral enterotoxin that mobilizes intracellular calcium, disrupting tight junction integrity and triggering chloride secretion independent of cAMP or cGMP pathways.

Question 158: A patient on warfarin presents with headache, confusion, and a hyperdense crescent-shaped lesion over the convexity on non-contrast CT. What is the diagnosis?

Intracerebral hemorrhage
Subarachnoid hemorrhage
Subdural hematoma (Correct answer)
Epidural hematoma

Correct answer: Subdural hematoma

A crescent-shaped hyperdense collection crossing suture lines over the brain convexity is the classic appearance of an acute subdural hematoma.

Question 159: A 60-year-old woman is found to have an elevated serum calcium level of 11.5 mg/dL on routine labs. A subsequent workup confirms primary hyperparathyroidism. Which of the following sets of laboratory findings is most characteristic of this condition?

Low serum calcium, high serum phosphate, high parathyroid hormone (PTH).
High serum calcium, high serum phosphate, low parathyroid hormone (PTH).
High serum calcium, low serum phosphate, low parathyroid hormone (PTH).
High serum calcium, low serum phosphate, high or inappropriately normal parathyroid hormone (PTH). (Correct answer)

Correct answer: High serum calcium, low serum phosphate, high or inappropriately normal parathyroid hormone (PTH).

In primary hyperparathyroidism, one or more parathyroid glands autonomously secrete excessive amounts of PTH. PTH acts to increase serum calcium (via bone resorption and renal reabsorption) and decrease serum phosphate (by increasing renal excretion). Therefore, the classic biochemical profile is hypercalcemia, hypophosphatemia, and an elevated or inappropriately normal PTH level (a normal PTH is inappropriate in the setting of hypercalcemia).

Question 160: A 65-year-old smoker presents with proximal limb weakness that improves with repeated muscle use. Reflexes are absent but return after exercise. What antibody mediates this condition?

Anti-voltage-gated calcium channel (VGCC) (Correct answer)
Anti-MuSK
Anti-AChR
Anti-GQ1b

Correct answer: Anti-voltage-gated calcium channel (VGCC)

Lambert-Eaton myasthenic syndrome is caused by anti-VGCC antibodies that reduce presynaptic acetylcholine release, often paraneoplastic with SCLC.

Question 161: Which finding on colonoscopy is most characteristic of Crohn's disease compared to ulcerative colitis?

Skip lesions with cobblestoning (Correct answer)
Continuous mucosal involvement from rectum
Pseudopolyps
Crypt abscesses on biopsy

Correct answer: Skip lesions with cobblestoning

Crohn's disease characteristically produces skip lesions with transmural inflammation, cobblestoning of the mucosa, and can affect any segment of the GI tract.

Question 162: A 55-year-old man presents with pain and stiffness in his shoulders and hips that is worse in the morning, elevated ESR, and normal muscle enzymes. He responds dramatically to low-dose prednisone. What is the diagnosis?

Giant cell arteritis
Polymyositis
Fibromyalgia
Polymyalgia rheumatica (Correct answer)

Correct answer: Polymyalgia rheumatica

Polymyalgia rheumatica presents with proximal girdle stiffness, markedly elevated ESR/CRP, normal CK, and a dramatic response to low-dose corticosteroids.

Question 163: A 35-year-old man with a history of intravenous drug use presents to the emergency department with a 2-day history of severe right knee pain, swelling, and an inability to bear weight. On examination, the knee is erythematous, warm, and exquisitely tender. He has a fever of 39.0°C (102.2°F). What is the most crucial next step in the diagnosis and management of this patient?

Obtain an MRI of the knee
Order blood cultures and C-reactive protein
Perform an immediate arthrocentesis (Correct answer)
Initiate empiric intravenous antibiotics

Correct answer: Perform an immediate arthrocentesis

The clinical presentation is highly suggestive of septic arthritis, which is a medical emergency requiring prompt diagnosis to prevent joint destruction. The most critical step is to perform an immediate joint aspiration (arthrocentesis). Analysis of the synovial fluid for cell count, Gram stain, and culture is essential to confirm the diagnosis and guide antibiotic therapy. While antibiotics, blood cultures, and imaging are all important, confirming the diagnosis via arthrocentesis is the highest priority and should ideally be done before starting antibiotics.

Question 164: A 70-year-old man cannot empty his bladder and has a post-void residual of 350 mL. PSA is elevated. What is the most likely cause?

Neurogenic bladder
Benign prostatic hyperplasia (Correct answer)
Urethral stricture
Detrusor overactivity

Correct answer: Benign prostatic hyperplasia

BPH causes bladder outlet obstruction in older men, leading to urinary retention and elevated post-void residual volumes.

Question 165: Stevens-Johnson Syndrome (SJS) is most commonly triggered by:

Autoimmune disease
Viral infections
Bacterial toxins
Drug reactions (Correct answer)

Correct answer: Drug reactions

Stevens-Johnson Syndrome is most commonly triggered by drug reactions, particularly sulfonamides, anticonvulsants, and NSAIDs.

Question 166: A 28-year-old woman presents with cyclic pelvic pain, dysmenorrhea, dyspareunia, and infertility. The most likely diagnosis is:

Uterine leiomyomas (fibroids)
Endometriosis (Correct answer)
Cervical stenosis
Polycystic ovarian syndrome

Correct answer: Endometriosis

The classic triad of dysmenorrhea, dyspareunia, and infertility in a reproductive-age woman strongly suggests endometriosis caused by ectopic endometrial implants.

Question 167: Allergic contact dermatitis is a type IV hypersensitivity reaction mediated by:

Neutrophil infiltration
IgG antibodies and complement
IgE antibodies and mast cells
T lymphocytes (delayed-type) (Correct answer)

Correct answer: T lymphocytes (delayed-type)

Allergic contact dermatitis is a type IV (cell-mediated/delayed-type) hypersensitivity reaction mediated by sensitized T lymphocytes.

Question 168: Which of the following histopathological findings is most characteristic of Crohn's disease and helps differentiate it from ulcerative colitis?

Crypt abscesses
Continuous inflammation limited to the mucosa
Non-caseating granulomas (Correct answer)
Pseudopolyps

Correct answer: Non-caseating granulomas

Non-caseating granulomas are a hallmark of Crohn's disease, found in a significant number of cases, and are not seen in ulcerative colitis. Their presence points to the transmural, granulomatous inflammation characteristic of Crohn's. Crypt abscesses and pseudopolyps can be seen in both conditions but are more typical of ulcerative colitis. Continuous inflammation limited to the mucosa is the classic description for ulcerative colitis, whereas Crohn's disease is characterized by discontinuous (skip lesions) and transmural inflammation.

Question 169: A 55-year-old presents with ipsilateral Horner syndrome, contralateral pain/temperature loss, ipsilateral facial numbness, dysphagia, and hoarseness. Which artery is occluded?

Posterior inferior cerebellar artery (Correct answer)
Middle cerebral artery
Basilar artery
Anterior spinal artery

Correct answer: Posterior inferior cerebellar artery

Lateral medullary (Wallenberg) syndrome results from PICA occlusion and presents with the described crossed sensory deficit and cranial nerve findings.

Question 170: A patient with idiopathic pulmonary fibrosis (IPF) shows progressive decline in FVC. Which medication has been shown to slow disease progression?

Azathioprine
N-acetylcysteine
Prednisone
Nintedanib (Correct answer)

Correct answer: Nintedanib

Nintedanib and pirfenidone are the only antifibrotic agents proven to slow FVC decline in IPF; prednisone and azathioprine are no longer recommended.

Question 171: A 45-year-old woman presents with weight gain, cold intolerance, constipation, and a TSH of 12 mIU/L with low free T4. What is the most appropriate treatment?

Radioactive iodine ablation
Methimazole
Liothyronine (T3) supplementation
Levothyroxine (T4) replacement (Correct answer)

Correct answer: Levothyroxine (T4) replacement

Primary hypothyroidism is treated with levothyroxine (synthetic T4), which is peripherally converted to the active T3 hormone.

Question 172: A 55-year-old woman with breast cancer develops bone pain and a corrected serum calcium of 13.8 mg/dL. The most likely mediator of humoral hypercalcemia of malignancy is:

1,25-dihydroxyvitamin D
PTHrP (Correct answer)
PTH
IL-1β

Correct answer: PTHrP

PTH-related protein (PTHrP) is secreted by many solid tumors and activates PTH receptors in bone and kidney, causing hypercalcemia without elevated true PTH.

Question 173: A 7-year-old boy presents with a palpable purpuric rash on his lower extremities, arthralgia, and abdominal pain. A urinalysis reveals microscopic hematuria and proteinuria. These findings are most consistent with which of the following conditions?

Post-streptococcal Glomerulonephritis
Minimal Change Disease
Alport Syndrome
Henoch-Schönlein Purpura (HSP) Nephritis (Correct answer)

Correct answer: Henoch-Schönlein Purpura (HSP) Nephritis

The clinical triad of a palpable purpuric rash (without thrombocytopenia), arthritis, and abdominal pain is characteristic of Henoch-Schönlein Purpura (HSP), an IgA-mediated small-vessel vasculitis. Renal involvement (HSP Nephritis) is common, occurring in up to 50% of patients, and typically manifests as hematuria and proteinuria due to glomerular inflammation.

Question 174: A 29-year-old female presents with an episode of unilateral vision loss and pain with eye movement that resolved over several weeks. Six months later, she develops numbness and tingling in her left leg. An MRI of the brain reveals multiple periventricular white matter lesions. A lumbar puncture is performed. Which cerebrospinal fluid (CSF) finding would be most supportive of a diagnosis of multiple sclerosis?

Low glucose, high protein, and marked neutrophilic pleocytosis
Presence of two or more IgG oligoclonal bands not present in the serum (Correct answer)
Xanthochromia and a high red blood cell count
Elevated protein with a normal cell count (albuminocytologic dissociation)

Correct answer: Presence of two or more IgG oligoclonal bands not present in the serum

The presence of two or more IgG oligoclonal bands in the cerebrospinal fluid that are not found in the patient's serum is a hallmark laboratory finding in multiple sclerosis, present in over 95% of patients. This indicates intrathecal (within the CNS) production of immunoglobulins, reflecting the inflammatory nature of the disease. Albuminocytologic dissociation is characteristic of Guillain-Barré syndrome. Low glucose and high neutrophils suggest bacterial meningitis. Xanthochromia points to a subarachnoid hemorrhage.

Question 175: Electrical alternans on ECG in a patient with hypotension and elevated JVP most likely indicates which condition?

Cardiac tamponade (Correct answer)
Hypertrophic cardiomyopathy
Pulmonary embolism
Constrictive pericarditis

Correct answer: Cardiac tamponade

Electrical alternans—beat-to-beat variation in QRS amplitude—results from the heart swinging within a large pericardial effusion, characteristic of cardiac tamponade.

Question 176: An 8-year-old child presents with pallor, jaundice, and splenomegaly. Peripheral smear shows spherocytes and reticulocytosis. The osmotic fragility test is positive. What is the inheritance pattern?

Mitochondrial
Autosomal recessive
Autosomal dominant (Correct answer)
X-linked recessive

Correct answer: Autosomal dominant

Hereditary spherocytosis is most commonly autosomal dominant (spectrin or ankyrin mutations), though autosomal recessive forms exist; autosomal dominant accounts for ~75% of cases.

Question 177: Aldosterone causes sodium retention primarily by upregulating which channel/transporter on the apical membrane of principal cells?

Na-Cl cotransporter (NCC)
Na/H exchanger (NHE3)
Epithelial sodium channel (ENaC) (Correct answer)
Na-K-2Cl cotransporter (NKCC2)

Correct answer: Epithelial sodium channel (ENaC)

Aldosterone increases transcription and membrane insertion of ENaC on principal cells of the collecting duct, promoting sodium reabsorption.

Question 178: A 45-year-old man has hypertension, hypokalemia, and a plasma aldosterone-to-renin ratio of 35 (elevated). What is the most likely diagnosis?

Cushing's syndrome
Primary hyperaldosteronism (Conn's syndrome) (Correct answer)
Pheochromocytoma
Renovascular hypertension

Correct answer: Primary hyperaldosteronism (Conn's syndrome)

An elevated aldosterone-to-renin ratio with hypokalemia and hypertension is the hallmark of primary hyperaldosteronism due to autonomous aldosterone secretion.

Question 179: A 55-year-old man with gout has recurrent attacks despite dietary modification. Serum uric acid is 9.8 mg/dL. Which enzyme deficiency would cause this hyperuricemia through overproduction rather than underexcretion?

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency (Correct answer)
Glucose-6-phosphatase deficiency
Adenosine deaminase deficiency
Purine nucleoside phosphorylase deficiency

Correct answer: Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency

HGPRT deficiency (Lesch-Nyhan syndrome partial form) leads to decreased purine salvage and excess de novo purine synthesis, causing uric acid overproduction.

Question 180: A 68-year-old male with small cell lung cancer is admitted with confusion and lethargy. His laboratory results are significant for a serum sodium of 118 mEq/L. Which of the following laboratory patterns is most consistent with the Syndrome of Inappropriate Antidiuretic Hormone (SIADH)?

Euvolemic hyponatremia, high urine osmolality (>100 mOsm/kg), high urine sodium (>40 mEq/L). (Correct answer)
Hypovolemic hyponatremia, high urine osmolality (>450 mOsm/kg), low urine sodium (<20 mEq/L).
Euvolemic hyponatremia, low urine osmolality (<100 mOsm/kg), high urine sodium (>40 mEq/L).
Hypervolemic hyponatremia, low urine osmolality (<100 mOsm/kg), low urine sodium (<20 mEq/L).

Correct answer: Euvolemic hyponatremia, high urine osmolality (>100 mOsm/kg), high urine sodium (>40 mEq/L).

The key features of SIADH are euvolemic hyponatremia due to excess free water retention. Despite the low serum osmolality, the urine is inappropriately concentrated (urine osmolality >100 mOsm/kg). The body attempts to excrete the excess fluid by promoting natriuresis, leading to a high urine sodium concentration (typically >40 mEq/L).

Question 181: A patient with moderate persistent asthma continues to have frequent exacerbations despite maximum-dose ICS/LABA. IgE is 450 IU/mL and blood eosinophils are 380 cells/μL. Which add-on biologic therapy is most appropriate?

Dupilumab (anti-IL-4Rα)
Benralizumab (anti-IL-5Rα)
Tezepelumab (anti-TSLP)
Omalizumab (anti-IgE) (Correct answer)

Correct answer: Omalizumab (anti-IgE)

Omalizumab is indicated for moderate-to-severe allergic asthma with elevated IgE and sensitivity to perennial allergens when uncontrolled on high-dose ICS/LABA.

Question 182: A patient with schizophrenia on haloperidol develops involuntary repetitive movements of the face, tongue, and extremities after 3 years of treatment. What is this condition?

Tardive dyskinesia (Correct answer)
Akathisia
Parkinsonism
Acute dystonia

Correct answer: Tardive dyskinesia

Tardive dyskinesia is a late-onset movement disorder from prolonged dopamine receptor blockade, typically presenting with oro-facial dyskinesias.

Question 183: A 65-year-old male with a long-standing history of type 2 diabetes and hypertension presents with fatigue, lower extremity edema, and a metallic taste in his mouth. Laboratory results show a GFR of 25 mL/min/1.73 m², serum potassium of 5.8 mEq/L, and BUN of 80 mg/dL. Which of the following medications that acts on the renal system is most likely contributing to his hyperkalemia?

Hydrochlorothiazide
Amlodipine
Lisinopril (Correct answer)
Furosemide

Correct answer: Lisinopril

Lisinopril, an ACE inhibitor, is a common cause of hyperkalemia in patients with chronic kidney disease (CKD). ACE inhibitors block the conversion of angiotensin I to angiotensin II, leading to decreased aldosterone secretion. Aldosterone is responsible for potassium excretion in the distal tubules, so its inhibition leads to potassium retention. Furosemide (a loop diuretic) and hydrochlorothiazide (a thiazide diuretic) both increase potassium excretion. Amlodipine, a calcium channel blocker, does not significantly affect potassium levels.

Question 184: Which of the following anti-epileptic drugs is contraindicated in juvenile myoclonic epilepsy due to risk of worsening seizures?

Levetiracetam
Carbamazepine (Correct answer)
Valproate
Lamotrigine

Correct answer: Carbamazepine

Carbamazepine and phenytoin can paradoxically worsen myoclonic and absence seizures in JME by blocking sodium channels that exacerbate this generalized epilepsy.

Question 185: A 70-year-old man has a hemoglobin of 8 g/dL, serum ferritin of 800 ng/mL, low TIBC, and elevated ESR. His anemia is most consistent with:

Anemia of chronic disease (Correct answer)
Iron deficiency anemia
Sideroblastic anemia
Hemolytic anemia

Correct answer: Anemia of chronic disease

Anemia of chronic disease features low iron, low TIBC, high ferritin (iron trapped in stores), and normal-to-low reticulocytes due to hepcidin-mediated sequestration.

Question 186: A 58-year-old male with acute myeloid leukemia is undergoing induction chemotherapy and develops profound neutropenia. He becomes febrile and develops pleuritic chest pain and a cough productive of blood-streaked sputum. A high-resolution CT scan of the chest reveals several nodules, one of which has a surrounding area of ground-glass opacity. This radiologic finding is known as the halo sign. Which of the following is the most likely causative organism?

Candida albicans
Aspergillus fumigatus (Correct answer)
Mycobacterium tuberculosis
Pneumocystis jirovecii

Correct answer: Aspergillus fumigatus

In a severely immunocompromised, neutropenic patient, the combination of fever, pleuritic chest pain, and hemoptysis with a CT finding of a pulmonary nodule surrounded by a halo of ground-glass attenuation is highly suggestive of invasive pulmonary aspergillosis (IPA). [4, 15, 16] The central nodule represents fungal-induced infarction, and the surrounding halo represents alveolar hemorrhage, characteristic of the angioinvasive nature of Aspergillus. [15]

Question 187: A 68-year-old male presents with a resting tremor in his right hand, bradykinesia, and rigidity. His symptoms have progressed slowly over the past two years. Which of the following is the primary pathophysiological mechanism responsible for this patient's motor symptoms?

Expansion of CAG trinucleotide repeats in the huntingtin gene
Degeneration of cholinergic neurons in the nucleus basalis of Meynert
Autoimmune demyelination of oligodendrocytes in the central nervous system
Loss of dopaminergic neurons in the substantia nigra pars compacta (Correct answer)

Correct answer: Loss of dopaminergic neurons in the substantia nigra pars compacta

The classic motor symptoms of Parkinson's disease—tremor, rigidity, and bradykinesia—are primarily caused by the progressive loss of dopamine-producing neurons in the substantia nigra pars compacta. This leads to a dopamine deficit in the striatum, disrupting the basal ganglia motor circuit. Cholinergic neuron loss is characteristic of Alzheimer's disease. Demyelination is the hallmark of multiple sclerosis. CAG repeat expansion causes Huntington's disease.

Question 188: Which mechanism explains the wide pulse pressure seen in aortic regurgitation?

Elevated systolic pressure from increased stroke volume and low diastolic pressure from regurgitant runoff (Correct answer)
Peripheral vasoconstriction raising systolic and diastolic pressure equally
Increased blood viscosity due to polycythemia
Decreased heart rate allowing greater diastolic filling

Correct answer: Elevated systolic pressure from increased stroke volume and low diastolic pressure from regurgitant runoff

In AR, the large forward stroke volume raises systolic pressure, while diastolic runoff back into the LV lowers diastolic pressure, widening the pulse pressure.

Question 189: Which test is most sensitive for detecting early iron deficiency before anemia develops?

MCV
Serum iron
Hemoglobin
Serum ferritin (Correct answer)

Correct answer: Serum ferritin

Serum ferritin falls first in iron deficiency, reflecting depleted iron stores before iron-restricted erythropoiesis and anemia develop.

Question 190: A pathologist is examining brain tissue from a patient who had severe dementia. The microscopic examination reveals numerous extracellular neuritic plaques and intracellular neurofibrillary tangles, particularly in the hippocampus and neocortex. These findings are the classic neuropathological hallmarks of which condition?

Lewy Body Dementia
Creutzfeldt-Jakob Disease
Huntington's Disease
Alzheimer's Disease (Correct answer)

Correct answer: Alzheimer's Disease

The two cardinal neuropathological lesions that define Alzheimer's Disease are extracellular plaques composed of beta-amyloid peptide and intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein. Lewy Body Dementia is characterized by alpha-synuclein aggregates (Lewy bodies). Creutzfeldt-Jakob disease shows spongiform changes and prion protein deposition. Huntington's disease is characterized by neuronal loss and gliosis in the caudate and putamen due to mutant huntingtin protein.

Question 191: A 35-year-old woman develops progressive dyspnea and bilateral hilar lymphadenopathy on chest X-ray. Biopsy shows noncaseating granulomas. Which finding would most strongly indicate need for systemic corticosteroid treatment?

Asymptomatic bilateral hilar adenopathy
Hypercalcemia with renal involvement (Correct answer)
Löfgren syndrome presentation
Erythema nodosum with arthralgia

Correct answer: Hypercalcemia with renal involvement

Hypercalcemia with renal involvement in sarcoidosis requires systemic corticosteroids to prevent nephrocalcinosis and renal failure.

Question 192: A 19-year-old woman has a BMI of 16.5, self-induced vomiting after eating, and an intense fear of weight gain despite being significantly underweight. She has secondary amenorrhea. What is the most likely diagnosis?

Anorexia nervosa, binge-eating/purging subtype (Correct answer)
Binge eating disorder
Bulimia nervosa
Avoidant/restrictive food intake disorder

Correct answer: Anorexia nervosa, binge-eating/purging subtype

Anorexia nervosa (binge-eating/purging subtype) is defined by significantly low body weight plus purging behaviors; the critically low BMI distinguishes it from bulimia nervosa, where patients are typically normal weight.

Question 193: The Bishop score is used clinically to assess:

Placental function and fetal well-being
Cervical favorability for labor induction (Correct answer)
Fetal lung maturity
Risk of gestational diabetes

Correct answer: Cervical favorability for labor induction

The Bishop score evaluates cervical dilation, effacement, station, consistency, and position to predict the likelihood of successful labor induction.

Question 194: Which skin finding is pathognomonic for early Lyme disease?

Target lesions (erythema multiforme)
Vesicular eruption on dermatomal distribution
Petechial purpuric rash
Erythema migrans (Correct answer)

Correct answer: Erythema migrans

Erythema migrans — an expanding annular rash with central clearing at the Ixodes tick bite site — is pathognomonic for Lyme disease caused by Borrelia burgdorferi.

Question 195: A 55-year-old man has an absolute eosinophil count of 6,000/μL for >6 months with evidence of cardiac damage. FISH reveals FIP1L1-PDGFRA fusion. First-line treatment is:

High-dose corticosteroids
Imatinib (Correct answer)
Hydroxyurea
Mepolizumab

Correct answer: Imatinib

FIP1L1-PDGFRA-positive hypereosinophilic syndrome responds dramatically to imatinib (a PDGFR kinase inhibitor), achieving complete remission in most cases.

Question 196: A patient has metabolic acidosis with a normal anion gap, hyperchloremia, and urine pH persistently above 5.5 despite acidemia. Which type of RTA is this?

Type I (distal) RTA (Correct answer)
Type II (proximal) RTA
Type IV RTA
Type III RTA

Correct answer: Type I (distal) RTA

Type I (distal) RTA is characterized by inability to acidify urine (pH >5.5) due to defective H+ secretion in the collecting duct, causing hyperchloremic metabolic acidosis.

Question 197: A 60-year-old presents with resting tremor, bradykinesia, and cogwheel rigidity. He also has orthostatic hypotension, REM sleep behavior disorder, and anosmia. What is the unifying diagnosis?

Parkinson disease (Correct answer)
Multiple system atrophy
Essential tremor
Drug-induced parkinsonism

Correct answer: Parkinson disease

The combination of motor parkinsonism with autonomic dysfunction, REM sleep behavior disorder, and anosmia is characteristic of Parkinson disease.

Question 198: A 45-year-old female is diagnosed with Autosomal Dominant Polycystic Kidney Disease (ADPKD) after an incidental finding of multiple bilateral renal cysts on an abdominal ultrasound. Which of the following is the most accurate description of the underlying pathophysiology of this condition?

Mutations in PKD1 or PKD2 genes, leading to abnormal ciliary function, altered tubular cell proliferation, and fluid secretion into cysts. (Correct answer)
Mutations in genes encoding for collagen type IV, leading to a weakened glomerular basement membrane.
Chronic obstruction of the urinary tract leading to back pressure and cystic dilation of the nephrons.
Deposition of immune complexes in the glomeruli, causing inflammatory damage and cyst formation.

Correct answer: Mutations in PKD1 or PKD2 genes, leading to abnormal ciliary function, altered tubular cell proliferation, and fluid secretion into cysts.

ADPKD is primarily caused by mutations in the PKD1 (encoding polycystin-1) or PKD2 (encoding polycystin-2) genes. These proteins are crucial for the normal function of renal tubular cilia, which act as mechanosensors. Dysfunction of these cilia leads to abnormal intracellular signaling (e.g., increased cAMP), resulting in increased cell proliferation, fluid secretion, and the progressive formation and enlargement of renal cysts.

Question 199: A patient develops Wolff-Parkinson-White syndrome with atrial fibrillation. Why is AV nodal blockade with diltiazem potentially lethal?

It prolongs the QT interval causing torsades de pointes
It causes paradoxical acceleration of AV nodal conduction
Slowing AV node conduction preferentially routes impulses down the accessory pathway at dangerously fast rates (Correct answer)
It causes direct myocardial depression leading to asystole

Correct answer: Slowing AV node conduction preferentially routes impulses down the accessory pathway at dangerously fast rates

Blocking the AV node in WPW-AF directs all impulses through the unprotected accessory pathway, which can conduct at rates exceeding 300 bpm, potentially degenerating into ventricular fibrillation.

Question 200: Ectopic pregnancy most commonly implants in which location?

Fallopian tube ampulla (Correct answer)
Ovary
Abdominal cavity
Cervix

Correct answer: Fallopian tube ampulla

Approximately 95% of ectopic pregnancies occur in the fallopian tube, with the ampullary segment (70%) being the most common implantation site.

Question 201: A 28-year-old woman in her third trimester develops severe headache, blurry vision, and BP of 160/110 mmHg. Urinalysis shows 3+ proteinuria. What is the most appropriate management?

Strict bed rest and oral antihypertensives only
Emergent cesarean section without medications
IV magnesium sulfate for seizure prophylaxis and delivery planning (Correct answer)
Observation and recheck in 24 hours

Correct answer: IV magnesium sulfate for seizure prophylaxis and delivery planning

Severe preeclampsia requires IV magnesium sulfate to prevent eclamptic seizures and antihypertensives, with delivery being the definitive treatment.

Question 202: What is the most common cause of first-trimester spontaneous abortion?

Chromosomal abnormalities (Correct answer)
Cervical incompetence
Antiphospholipid syndrome
Uterine anomalies

Correct answer: Chromosomal abnormalities

Chromosomal abnormalities, most commonly trisomies due to meiotic non-disjunction, account for approximately 50-60% of first-trimester spontaneous abortions.

Question 203: A 50-year-old woman with rheumatoid arthritis develops a vasculitic rash, peripheral neuropathy, and digital gangrene. Which complication of RA does she have?

Caplan syndrome
Sjögren overlap syndrome
Rheumatoid vasculitis (Correct answer)
Felty syndrome

Correct answer: Rheumatoid vasculitis

Rheumatoid vasculitis is a rare but serious extra-articular complication of severe RA characterized by inflammation of small-to-medium vessels causing neuropathy, skin ulcers, and digital ischemia.

Question 204: A 60-year-old construction worker in the Southwest US develops fever, chest pain, eosinophilia, and a coin lesion on CXR after exposure to soil dust. Serology is positive. Which organism is responsible?

Aspergillus fumigatus
Histoplasma capsulatum
Blastomyces dermatitidis
Coccidioides immitis (Correct answer)

Correct answer: Coccidioides immitis

Coccidioides immitis is endemic to the arid Southwest US (San Joaquin Valley fever) and causes pulmonary infection with eosinophilia; large endosporulating spherules are the tissue form.

Question 205: A 35-year-old woman presents with episodic unilateral headache, nausea, photophobia, and phonophobia lasting 4-72 hours. She notes visual aura preceding attacks. What is the classification?

Trigeminal neuralgia
Tension-type headache
Cluster headache
Migraine with aura (Correct answer)

Correct answer: Migraine with aura

Recurrent unilateral headache with nausea, photophobia, and preceding visual aura fulfills criteria for migraine with aura.

Question 206: False regarding the expression of Eukaryotic genes in the cytosol is:

Capping helps in attachment of mRNA to 40 S Ribosome
Releasing factor releases the polypeptide chain from the P site
EF2 shifts between GDP & GTP
N formyl methionine tRNA will be the first t-RNA to come into action (Correct answer)

Correct answer: N formyl methionine tRNA will be the first t-RNA to come into action

This statement is false because N-formylmethionine tRNA (fMet-tRNA) is the initiator tRNA in *prokaryotic* protein synthesis. In *eukaryotic* gene expression, the first tRNA to come into action is methionine tRNA (Met-tRNA), which carries an unformylated methionine. The other options describe true aspects of eukaryotic translation.

Question 207: A 66-year-old man presents with progressive exertional dyspnea, bibasilar crackles, and digital clubbing. CT chest shows bilateral basal-predominant honeycombing and traction bronchiectasis. Pulmonary function tests reveal a restrictive pattern with reduced DLCO. What is the most likely diagnosis?

Hypersensitivity pneumonitis
Cryptogenic organizing pneumonia
Idiopathic pulmonary fibrosis (Correct answer)
Sarcoidosis

Correct answer: Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) presents in older men with progressive dyspnea, Velcro crackles, clubbing, and CT showing UIP pattern (honeycombing with basal-predominant traction bronchiectasis).

Question 208: A 55-year-old woman presents with episodic right upper quadrant pain, nausea, and jaundice following fatty meals. Ultrasound shows gallstones. Which composition of gallstones is most common in the United States?

Pigment (brown) stones
Calcium bilirubinate stones
Cholesterol stones (Correct answer)
Pigment (black) stones

Correct answer: Cholesterol stones

Cholesterol gallstones account for approximately 80% of gallstones in the US and are associated with obesity, female sex, pregnancy, and rapid weight loss.

Question 209: A pathologist examining a lymph node biopsy from a 24-year-old male with painless cervical lymphadenopathy identifies large, binucleated cells with prominent eosinophilic nucleoli, described as having an 'owl's eye' appearance. These cells are scattered within a background of reactive lymphocytes, eosinophils, and plasma cells. This pathognomonic finding is diagnostic of which malignancy?

Follicular lymphoma
Chronic lymphocytic leukemia (CLL)
Burkitt lymphoma
Classical Hodgkin lymphoma (Correct answer)

Correct answer: Classical Hodgkin lymphoma

The described cell is a classic Reed-Sternberg cell, which is the pathognomonic hallmark of classical Hodgkin lymphoma. The 'owl's eye' appearance is due to its large size, binucleation, and prominent, inclusion-like nucleoli. The presence of these cells within a mixed inflammatory background is essential for the diagnosis.

Question 210: A 60-year-old man presents with difficulty swallowing, regurgitation of food eaten hours earlier, and a gurgling mass in the neck. Barium swallow shows a posterior pharyngeal outpouching. What is the diagnosis?

Esophageal web
Achalasia
Diffuse esophageal spasm
Zenker's diverticulum (Correct answer)

Correct answer: Zenker's diverticulum

Zenker's diverticulum is a false diverticulum (pulsion type) at Killian's triangle in the posterior hypopharynx, causing regurgitation of undigested food and a palpable neck mass.

Question 211: A 28-year-old traveler to Mexico develops profuse watery 'rice-water' diarrhea with no fecal leukocytes. The causative organism produces a toxin that permanently activates Gs protein by ADP-ribosylation. Which organism?

Salmonella typhi
Campylobacter jejuni
Enterotoxigenic E. coli
Vibrio cholerae (Correct answer)

Correct answer: Vibrio cholerae

Vibrio cholerae produces cholera toxin, which ADP-ribosylates the Gs alpha subunit, locking adenylyl cyclase in the 'on' position, causing massive cAMP-driven chloride and water secretion.

Question 212: A patient with chronic kidney disease has a GFR of 20 mL/min. Which acid-base disorder is most expected?

Metabolic alkalosis
Respiratory alkalosis
High anion gap metabolic acidosis (Correct answer)
Hyperchloremic normal anion gap acidosis

Correct answer: High anion gap metabolic acidosis

Chronic kidney disease causes accumulation of unmeasured anions (sulfate, phosphate, organic acids) leading to high anion gap metabolic acidosis.

Question 213: Preeclampsia is defined as new-onset hypertension (≥140/90 mmHg) after 20 weeks gestation with:

Facial edema and headache
Fetal growth restriction only
Proteinuria or end-organ damage (Correct answer)
Elevated serum hCG

Correct answer: Proteinuria or end-organ damage

Preeclampsia is defined as new-onset hypertension of ≥140/90 mmHg after 20 weeks with either significant proteinuria (≥300 mg/24h) or end-organ dysfunction.

Question 214: A 62-year-old presents with sudden pleuritic chest pain and dyspnea. CT pulmonary angiography confirms bilateral pulmonary emboli. HR is 118, BP is 98/60, troponin is elevated. What is the most appropriate immediate management?

Surgical embolectomy
Systemic thrombolysis with alteplase (Correct answer)
Anticoagulation with heparin alone
Catheter-directed thrombolysis

Correct answer: Systemic thrombolysis with alteplase

Massive PE with hemodynamic instability and no contraindications warrants systemic thrombolysis as it provides the fastest clot lysis.

Question 215: A 48-year-old man presents with fatigue, bronze skin discoloration, elevated liver enzymes, and diabetes. Serum ferritin is 2,800 ng/mL and transferrin saturation is 72%. What is the most likely diagnosis?

Hereditary hemochromatosis (Correct answer)
Alcoholic hepatitis
Hemolytic anemia
Wilson's disease

Correct answer: Hereditary hemochromatosis

Hereditary hemochromatosis (HFE gene mutation) presents with iron overload causing liver disease, diabetes, skin bronzing, and cardiomyopathy; transferrin saturation >45% is a key screening marker.

Question 216: A patient develops fever, productive cough, and consolidation 5 days after intubation for trauma. BAL culture grows Pseudomonas aeruginosa. Which antibiotic regimen is most appropriate?

Levofloxacin monotherapy
Vancomycin plus piperacillin-tazobactam
Meropenem monotherapy
Cefepime plus tobramycin (Correct answer)

Correct answer: Cefepime plus tobramycin

Ventilator-associated pneumonia caused by Pseudomonas requires double-coverage with an antipseudomonal beta-lactam plus an aminoglycoside or fluoroquinolone to reduce resistance risk.

Question 217: A 32-year-old man presents with painless cervical lymphadenopathy. Biopsy reveals Reed-Sternberg cells with owl-eye nucleoli in a background of lymphocytes. Which immunophenotype is characteristic of these cells?

CD15+, CD30+, CD45− (Correct answer)
CD10+, BCL2+
CD20+, CD3−
CD5+, CD23+

Correct answer: CD15+, CD30+, CD45−

Reed-Sternberg cells in classical Hodgkin lymphoma are CD15+/CD30+ and characteristically CD45− (leukocyte common antigen negative).

Question 218: A patient with acute leukemia develops a prolonged PT, aPTT, low fibrinogen, elevated D-dimer, and thrombocytopenia. Which leukemia subtype is classically associated with this coagulopathy?

AML-M2 (with t(8;21))
AML-M3 (APL with t(15;17)) (Correct answer)
ALL (B-cell)
CML blast crisis

Correct answer: AML-M3 (APL with t(15;17))

Acute promyelocytic leukemia (APL/AML-M3) releases procoagulants from granules causing DIC; ATRA is urgently needed before cytotoxic chemotherapy.

Question 219: Which classic description applies to varicella (chickenpox) skin lesions?

Silvery-scaled papules on elbows
Honey-colored crusted vesicles
Dew drops on a rose petal (Correct answer)
Target lesions with central clearing

Correct answer: Dew drops on a rose petal

Varicella lesions are classically described as 'dew drops on a rose petal' — clear vesicles on an erythematous base at various stages of evolution.

Question 220: A 72-year-old patient is being evaluated for suspected idiopathic pulmonary fibrosis (IPF). Which of the following findings on high-resolution computed tomography (HRCT) of the chest is most characteristic of a 'definite UIP' (Usual Interstitial Pneumonia) pattern, often allowing for a confident diagnosis of IPF without a lung biopsy?

Subpleural, basal predominant honeycombing and traction bronchiectasis. (Correct answer)
Predominantly upper lobe ground-glass opacities and micronodules.
Peribronchovascular-centered reticulation with sparing of the subpleural lung.
Widespread consolidation and pleural effusions.

Correct answer: Subpleural, basal predominant honeycombing and traction bronchiectasis.

The hallmark of a definite Usual Interstitial Pneumonia (UIP) pattern on HRCT, which is the radiologic signature of IPF, is the presence of subpleural and basal predominant reticular abnormalities, honeycombing, and traction bronchiectasis. The other patterns described are inconsistent with a UIP pattern and suggest alternative diagnoses.

Question 221: A patient develops ascending paralysis 2 weeks after a GI infection with Campylobacter jejuni. CSF shows albuminocytologic dissociation. Which antibody is associated with this variant?

Anti-GM1 (Correct answer)
Anti-GQ1b
Anti-MAG
Anti-GD1b

Correct answer: Anti-GM1

Anti-GM1 antibodies are associated with the acute motor axonal neuropathy (AMAN) variant of Guillain-Barré syndrome linked to Campylobacter.

Question 222: Which antibiotic is first-line treatment for uncomplicated cellulitis in a non-penicillin-allergic patient?

Doxycycline
Vancomycin
Cephalexin (Correct answer)
Clindamycin

Correct answer: Cephalexin

Cephalexin (a first-generation cephalosporin) is first-line oral therapy for uncomplicated cellulitis caused by streptococci and methicillin-susceptible staphylococci.

Question 223: Which initial test is most sensitive for diagnosing ectopic pregnancy?

Serum quantitative beta-hCG (Correct answer)
Transvaginal ultrasound
Diagnostic laparoscopy
Urine pregnancy test

Correct answer: Serum quantitative beta-hCG

Serum quantitative beta-hCG is the most sensitive initial test; in ectopic pregnancy, levels typically fail to double every 48 hours as expected in a normal IUP.

Question 224: A 40-year-old man with ankylosing spondylitis has failed NSAIDs. Which biologic class is most effective for his axial disease?

B-cell depletion agents (e.g., rituximab)
IL-6 receptor antagonists (e.g., tocilizumab)
CTLA-4 Ig fusion proteins (e.g., abatacept)
TNF-alpha inhibitors (e.g., adalimumab) (Correct answer)

Correct answer: TNF-alpha inhibitors (e.g., adalimumab)

TNF-alpha inhibitors are first-line biologics for ankylosing spondylitis refractory to NSAIDs; IL-17 inhibitors are an alternative, but IL-6 and rituximab show limited efficacy for axial disease.

Question 225: A 65-year-old man presents with change in bowel habits, hematochezia, and a 15-pound weight loss over 3 months. Colonoscopy reveals a mass in the sigmoid colon. Which molecular pathway is most commonly altered in sporadic colorectal cancer?

APC/Wnt pathway (chromosomal instability) (Correct answer)
BRAF mutation pathway
TGF-β signaling pathway
Microsatellite instability pathway (MMR deficiency)

Correct answer: APC/Wnt pathway (chromosomal instability)

The chromosomal instability pathway involving APC tumor suppressor gene mutation is the most common pathway in sporadic colorectal cancer, driving the adenoma-carcinoma sequence.

Question 226: A 35-year-old HIV-positive patient with a CD4 count of 50 cells/μL presents with headache and fever. CSF India ink preparation reveals encapsulated yeast. Which organism is responsible?

Candida albicans
Histoplasma capsulatum
Cryptococcus neoformans (Correct answer)
Aspergillus fumigatus

Correct answer: Cryptococcus neoformans

Cryptococcus neoformans causes meningitis in severely immunocompromised patients and is identified by India ink staining showing a large polysaccharide capsule.

Question 227: A patient presents with severe hyponatremia (Na 118 mEq/L) and is asymptomatic. Urine osmolality is 600 mOsm/kg and urine Na is 55 mEq/L. Serum osmolality is low. What is the most likely cause?

Adrenal insufficiency
Hypothyroidism
Primary polydipsia
SIADH (Correct answer)

Correct answer: SIADH

SIADH presents with euvolemic hyponatremia, inappropriately concentrated urine (>100 mOsm/kg), and high urine sodium (>40 mEq/L), reflecting inappropriate ADH secretion.

Question 228: A 60-year-old woman on long-term corticosteroids develops back pain. DEXA scan shows T-score of -2.8. Which medication addresses the underlying pathophysiology of her bone loss?

Calcitonin
Calcium supplementation alone
Alendronate (bisphosphonate) (Correct answer)
Vitamin D supplementation alone

Correct answer: Alendronate (bisphosphonate)

Bisphosphonates inhibit osteoclast-mediated bone resorption and are first-line for glucocorticoid-induced osteoporosis with T-score ≤-2.5.

Question 229: Which ventilator setting change is most appropriate for a patient with ARDS who develops worsening hypoxemia despite FiO2 of 0.6 and PEEP of 10 cmH2O?

Switch to pressure control ventilation
Increase PEEP to 14-16 cmH2O (Correct answer)
Increase tidal volume to 10 mL/kg IBW
Administer inhaled nitric oxide as first-line rescue

Correct answer: Increase PEEP to 14-16 cmH2O

Increasing PEEP improves oxygenation in ARDS by recruiting atelectatic alveoli while maintaining lung-protective tidal volumes of 4-6 mL/kg IBW.

Question 230: A 30-year-old woman presents with intermittent diplopia, ptosis worsening through the day, and proximal limb weakness. Ice pack test improves ptosis. What antibody should be ordered first?

Anti-voltage-gated calcium channel
Anti-LGI1
Anti-MuSK
Anti-AChR (Correct answer)

Correct answer: Anti-AChR

Anti-acetylcholine receptor (AChR) antibodies are positive in ~85% of generalized myasthenia gravis cases and are the first-line test.

Question 231: A 40-year-old develops ascending flaccid paralysis starting in both legs 2 weeks after a GI illness with Campylobacter jejuni. CSF shows elevated protein with normal cell count (albuminocytologic dissociation). Which condition is this?

Guillain-Barré syndrome (Correct answer)
Transverse myelitis
Botulism
West Nile virus encephalitis

Correct answer: Guillain-Barré syndrome

Guillain-Barré syndrome is a post-infectious demyelinating polyneuropathy often triggered by C. jejuni due to molecular mimicry between gangliosides and bacterial lipooligosaccharide; CSF shows albuminocytologic dissociation.

Question 232: Which finding on urinalysis is most consistent with acute tubular necrosis?

Muddy brown granular casts (Correct answer)
RBC casts
WBC casts
Oval fat bodies

Correct answer: Muddy brown granular casts

ATN causes sloughing of tubular epithelial cells that form muddy brown granular casts, which are pathognomonic for this condition.

Question 233: The most critical initial step in managing toxic epidermal necrolysis (TEN) is:

High-dose IV corticosteroids
Discontinue the offending drug and transfer to a burn unit (Correct answer)
Immediate IVIG infusion
Systemic broad-spectrum antibiotics

Correct answer: Discontinue the offending drug and transfer to a burn unit

Immediate discontinuation of the causative drug followed by supportive care in a specialized burn unit is the cornerstone of TEN management.

Question 234: A 22-year-old male presents to a sexual health clinic with a two-day history of purulent urethral discharge and dysuria. A Gram stain is performed on a smear of the discharge. Which of the following microscopic findings would be most diagnostic for Neisseria gonorrhoeae infection in this patient?

Gram-negative rods arranged in a 'school of fish' pattern
Absence of organisms but numerous polymorphonuclear leukocytes
Gram-positive cocci in chains
Gram-negative diplococci located within neutrophils (Correct answer)

Correct answer: Gram-negative diplococci located within neutrophils

The classic and highly specific Gram stain finding for urethritis caused by Neisseria gonorrhoeae in a symptomatic male is the presence of gram-negative (pink/red) diplococci (cocci in pairs, often kidney-bean shaped) inside of polymorphonuclear leukocytes (neutrophils). [11, 21, 33] This finding has a high sensitivity (>95%) and specificity (>99%) in this clinical context. [37]

Question 235: A 22-year-old woman has a lifelong history of heavy menstrual bleeding, prolonged bleeding after dental procedures, and a normal PT and platelet count but prolonged aPTT and PFA-100 closure time. von Willebrand factor antigen is 35% (low). What is the most likely diagnosis?

Bernard-Soulier syndrome
Type 1 von Willebrand disease (Correct answer)
Glanzmann thrombasthenia
Hemophilia A

Correct answer: Type 1 von Willebrand disease

Type 1 VWD is the most common inherited bleeding disorder, characterized by quantitative reduction of VWF causing mucocutaneous bleeding with prolonged PFA-100 and aPTT.

Question 236: A 55-year-old man with alcoholic cirrhosis develops sudden onset confusion, asterixis, and somnolence. Ammonia level is elevated. Which mechanism best explains hepatic encephalopathy?

Direct ethanol neurotoxicity
Hypoglycemia from impaired gluconeogenesis
Accumulation of nitrogenous waste products impairing cerebral function (Correct answer)
Cerebral edema from hyponatremia

Correct answer: Accumulation of nitrogenous waste products impairing cerebral function

Hepatic encephalopathy results from the failing liver's inability to detoxify ammonia and other nitrogenous compounds derived from gut bacteria and protein metabolism, causing neurological dysfunction.

Question 237: A 35-year-old woman with SLE develops proximal muscle weakness and a heliotrope rash around her eyes. Creatine kinase is markedly elevated. Which autoantibody is most specific for her inflammatory myopathy?

Anti-dsDNA
Anti-Ro/SSA
Anti-Jo-1 (Correct answer)
Anti-Smith

Correct answer: Anti-Jo-1

Anti-Jo-1 (anti-synthetase antibody) is the most specific marker for polymyositis/dermatomyositis and is associated with interstitial lung disease.

Question 238: A neonate develops purulent conjunctivitis within 2-4 days of birth. Gram stain of discharge shows gram-negative diplococci inside neutrophils. Which prophylactic agent should have been administered at birth?

Erythromycin ophthalmic ointment (Correct answer)
Silver nitrate drops
Acyclovir eye drops
Tetracycline ointment

Correct answer: Erythromycin ophthalmic ointment

Neonatal gonococcal ophthalmia (ophthalmia neonatorum) from N. gonorrhoeae is prevented by erythromycin ophthalmic ointment, the current US standard prophylaxis.

Question 239: HELLP syndrome is characterized by which triad of findings?

High hematocrit, Elevated LDH, Low potassium
Hemolysis, Elevated Liver enzymes, Low Platelets (Correct answer)
Hyperglycemia, Elevated lipids, Low albumin
Hypertension, Edema, Low protein

Correct answer: Hemolysis, Elevated Liver enzymes, Low Platelets

HELLP syndrome is defined by Hemolysis (microangiopathic), Elevated Liver enzymes, and Low Platelets (<100,000/μL) — a life-threatening complication of preeclampsia.

Question 240: A patient with moderate persistent asthma is well-controlled on medium-dose ICS/LABA. She is planning pregnancy. What is the most appropriate medication adjustment?

Switch to montelukast monotherapy
Reduce to low-dose ICS only
Continue current regimen (Correct answer)
Discontinue LABA and continue ICS alone

Correct answer: Continue current regimen

Well-controlled asthma during pregnancy should be maintained on current therapy, as uncontrolled asthma poses greater risk to mother and fetus than ICS/LABA.

Question 241: Long QT syndrome predisposes to torsades de pointes. Which underlying mechanism is common to both congenital and acquired forms?

Reduced repolarizing current (IKr) prolonging phase 3 of the action potential (Correct answer)
Enhanced calcium release from the sarcoplasmic reticulum
Increased automaticity in Purkinje fibers
Increased sodium influx shortening the action potential plateau

Correct answer: Reduced repolarizing current (IKr) prolonging phase 3 of the action potential

Both congenital LQTS (e.g., KCNQ1, HERG mutations) and drug-induced forms reduce the rapid delayed rectifier potassium current (IKr), prolonging repolarization and QT interval.

Question 242: A patient with multiple myeloma shows a serum M-spike on SPEP. Which immunoglobulin heavy chain is most commonly involved in multiple myeloma?

IgA
IgD
IgM
IgG (Correct answer)

Correct answer: IgG

IgG myeloma is the most common subtype, accounting for approximately 50–60% of multiple myeloma cases.

Question 243: A 35-year-old woman with SLE has red cell casts and nephritic syndrome. Biopsy shows wire loop lesions and subendothelial deposits. What class of lupus nephritis is this?

Class V (membranous)
Class III (focal proliferative)
Class II (mesangial proliferative)
Class IV (diffuse proliferative) (Correct answer)

Correct answer: Class IV (diffuse proliferative)

Class IV lupus nephritis is the most severe form, characterized by diffuse proliferative changes with wire loop lesions from subendothelial immune complex deposits.

Question 244: A 55-year-old man with limited cutaneous systemic sclerosis presents with Raynaud phenomenon, telangiectasias, and pulmonary hypertension. Which antibody is most commonly associated with this subset?

Anti-centromere antibody (Correct answer)
Anti-dsDNA
Anti-Jo-1
Anti-Scl-70 (topoisomerase I)

Correct answer: Anti-centromere antibody

Anti-centromere antibodies are characteristically associated with limited cutaneous systemic sclerosis (formerly CREST syndrome).

Question 245: On peripheral smear, teardrop cells (dacrocytes), nucleated RBCs, and immature granulocytes are seen together. This leukoerythroblastic picture is classic for:

G6PD hemolysis
Autoimmune hemolytic anemia
Myelophthisic anemia / myelofibrosis (Correct answer)
Megaloblastic anemia

Correct answer: Myelophthisic anemia / myelofibrosis

Myelofibrosis or bone marrow infiltration (myelophthisis) causes a leukoerythroblastic smear with teardrop cells as RBCs are squeezed through fibrotic marrow.

Question 246: A 68-year-old male with a significant smoking history presents with increased dyspnea, cough, and sputum production. His baseline is managed with a LAMA/LABA inhaler. He has had two moderate exacerbations in the past year. According to the most recent GOLD guidelines, what is the most appropriate next step in managing his stable COPD?

Add an inhaled corticosteroid (ICS) to his current regimen. (Correct answer)
Switch to a short-acting beta-agonist (SABA) as needed.
Prescribe a daily macrolide antibiotic.
Initiate long-term oral corticosteroid therapy.

Correct answer: Add an inhaled corticosteroid (ICS) to his current regimen.

According to the GOLD 2024 report, for a patient with persistent exacerbations on LAMA/LABA therapy, particularly with a history of ≥2 moderate exacerbations in the last year, the next step is to add an inhaled corticosteroid (ICS), creating a triple therapy regimen (LAMA/LABA/ICS). SABA is for rescue use, not maintenance. Long-term oral corticosteroids have significant side effects and are not recommended for stable management. Daily macrolides are considered for former smokers with persistent exacerbations but after triple therapy has been optimized.

Question 247: A 45-year-old female presents with a 6-month history of symmetric pain and swelling in her metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints, associated with morning stiffness lasting over an hour. Which of the following laboratory findings is most specific for the diagnosis of rheumatoid arthritis?

Positive anti-cyclic citrullinated peptide (anti-CCP) antibody (Correct answer)
Positive antinuclear antibody (ANA)
Elevated C-reactive protein (CRP)
Elevated rheumatoid factor (RF)

Correct answer: Positive anti-cyclic citrullinated peptide (anti-CCP) antibody

While RF, CRP, and ANA can be positive in rheumatoid arthritis, anti-CCP antibodies have the highest specificity (around 95-98%) for the disease. RF can be positive in other autoimmune diseases, infections, and even healthy individuals. CRP is a nonspecific marker of inflammation. ANA is more characteristic of SLE but can be seen in RA.

Question 248: Which pulmonary function pattern is most consistent with a diagnosis of hypersensitivity pneumonitis?

Obstructive pattern with air trapping
Mixed obstructive-restrictive with normal DLCO
Normal spirometry with elevated TLC
Restrictive pattern with reduced DLCO (Correct answer)

Correct answer: Restrictive pattern with reduced DLCO

Hypersensitivity pneumonitis typically produces a restrictive pattern with reduced DLCO due to interstitial inflammation and fibrosis.

Question 249: The Papez circuit's implicated nucleus is?

Anterior nucleus of thalamus (Correct answer)
Infralaminar
VPL nucleus
Pulvinar

Correct answer: Anterior nucleus of thalamus

The Papez circuit is a neural pathway involved in emotion and memory, particularly the formation of long-term memories. Key structures in this circuit include the hippocampus, fornix, mammillary bodies, mammillothalamic tract, anterior nucleus of the thalamus, cingulate gyrus, and entorhinal cortex. The anterior nucleus of the thalamus serves as a crucial relay station within this circuit.

Question 250: A patient has hyponatremia, inappropriately concentrated urine (>100 mOsm/kg), and normal volume status with no edema or dehydration. Serum uric acid and BUN are low. What is the diagnosis?

Psychogenic polydipsia
Cerebral salt wasting
Hypothyroidism
SIADH (Correct answer)

Correct answer: SIADH

SIADH presents with euvolemic hyponatremia, concentrated urine despite low serum osmolality, and dilute serum markers (low BUN, uric acid) due to water retention.

Question 251: A 32-year-old woman experiences recurrent unexpected panic attacks and has persistent worry about future attacks for 3 months. She avoids crowded places and public transportation. What is the most likely diagnosis?

Panic Disorder with Agoraphobia (Correct answer)
Social Anxiety Disorder
Generalized Anxiety Disorder
Specific Phobia

Correct answer: Panic Disorder with Agoraphobia

Panic disorder is characterized by recurrent unexpected panic attacks with persistent concern about future attacks; when accompanied by avoidance of situations where escape would be difficult, agoraphobia is also diagnosed.

Question 252: A 72-year-old with COPD and recurrent exacerbations (3 in past year) has FEV1 of 35% predicted and blood eosinophils of 320 cells/μL on dual LABA/LAMA therapy. Which is the most appropriate step-up?

Start azithromycin prophylaxis
Initiate long-term oral corticosteroids
Add inhaled corticosteroid (triple therapy) (Correct answer)
Add roflumilast

Correct answer: Add inhaled corticosteroid (triple therapy)

In COPD patients with frequent exacerbations and eosinophil count ≥300 cells/μL on dual bronchodilation, adding ICS (triple therapy) reduces exacerbation frequency.

Question 253: The term 'aphasia' refers to:

Loss of muscle function
Loss of vision
Loss of language ability (Correct answer)
Loss of hearing

Correct answer: Loss of language ability

A- (without) + -phasia (speech) = loss or impairment of language and speech.

Question 254: A 55-year-old pigeon handler develops progressive pneumonia with relative bradycardia (pulse-temperature dissociation), dry cough, and hyponatremia. CXR shows patchy infiltrates. Which organism causes this atypical pneumonia?

Chlamydophila psittaci
Legionella pneumophila (Correct answer)
Coxiella burnetii
Mycoplasma pneumoniae

Correct answer: Legionella pneumophila

Legionella pneumophila causes Legionnaires' disease, characterized by relative bradycardia, hyponatremia, diarrhea, and pontiac fever-like prodrome; it grows in water-cooling systems and causes lobar pneumonia.

Question 255: A 55-year-old with HIV presents with focal neurological deficits. MRI shows multiple ring-enhancing lesions. Toxoplasma serology is negative. What diagnosis must be excluded?

Primary CNS lymphoma (Correct answer)
Glioblastoma multiforme
Metastatic carcinoma
Bacterial brain abscess

Correct answer: Primary CNS lymphoma

In HIV patients with negative toxoplasma serology, primary CNS lymphoma is the leading differential for ring-enhancing lesions.

Question 256: Tinea versicolor (pityriasis versicolor) is caused by which organism?

Trichophyton rubrum
Malassezia furfur (Correct answer)
Epidermophyton floccosum
Candida albicans

Correct answer: Malassezia furfur

Tinea versicolor is caused by Malassezia furfur, a lipophilic dimorphic yeast that normally colonizes the skin's stratum corneum.

Question 257: A patient with longstanding type 2 diabetes presents with distal symmetric burning pain and loss of vibration sense in the feet. Which pathway is primarily damaged?

Dorsal columns and small unmyelinated C-fibers (Correct answer)
Corticospinal tract
Spinocerebellar tract
Anterior spinothalamic tract

Correct answer: Dorsal columns and small unmyelinated C-fibers

Diabetic peripheral neuropathy affects both small fibers (pain/temperature, C-fibers) and large fibers (vibration, dorsal column) in a length-dependent pattern.

Question 258: A 25-year-old with hematuria and sensorineural hearing loss has a family history of renal failure. Biopsy shows thinning and splitting of the GBM in a 'basket-weave' pattern. What is the diagnosis?

IgA nephropathy
Thin basement membrane disease
Alport syndrome (Correct answer)
Anti-GBM disease

Correct answer: Alport syndrome

Alport syndrome (X-linked, COL4A5 mutation) presents with hematuria, sensorineural deafness, and ocular abnormalities with characteristic GBM lamellation on EM.

Question 259: A 40-year-old woman develops microangiopathic hemolytic anemia, thrombocytopenia, fever, renal failure, and neurological symptoms. ADAMTS13 activity is <5%. What is the diagnosis?

Thrombotic thrombocytopenic purpura (Correct answer)
DIC
Hemolytic uremic syndrome
Evans syndrome

Correct answer: Thrombotic thrombocytopenic purpura

TTP is caused by ADAMTS13 deficiency (activity <10%), leading to ultra-large vWF multimers and platelet microthrombi causing the pentad of features.

Question 260: A 30-year-old man has episodic hypertension, headache, and diaphoresis. 24-hour urine shows elevated metanephrines. Which imaging is the BEST next step?

Nuclear bone scan
MRI of the adrenal glands (Correct answer)
CT chest
PET-CT of the pelvis

Correct answer: MRI of the adrenal glands

MRI of the adrenal glands is preferred for localizing pheochromocytoma due to its superior soft-tissue contrast and avoidance of iodinated contrast.

Question 261: A 68-year-old man with painless jaundice, clay-colored stools, and a palpable, non-tender gallbladder is most likely to have which diagnosis?

Acute cholecystitis
Primary sclerosing cholangitis
Carcinoma of the head of the pancreas (Correct answer)
Choledocholithiasis

Correct answer: Carcinoma of the head of the pancreas

Painless jaundice with a palpable, non-tender gallbladder (Courvoisier's sign) strongly suggests malignant biliary obstruction, most commonly pancreatic head carcinoma.

Question 262: A patient with polycystic kidney disease asks about the risk to their children. What is the inheritance pattern of autosomal dominant PKD?

X-linked dominant, 50% risk to sons
Autosomal recessive, 25% risk
Mitochondrial, 100% maternal transmission
Autosomal dominant, 50% risk to each child (Correct answer)

Correct answer: Autosomal dominant, 50% risk to each child

ADPKD (PKD1/PKD2 mutations) follows autosomal dominant inheritance with 50% probability of transmission to each offspring.

Question 263: A 48-year-old woman with systemic lupus erythematosus develops pleuritic chest pain and friction rub. Libman-Sacks endocarditis in SLE most commonly affects which valve?

Aortic valve (aortic stenosis)
Mitral valve (mitral regurgitation) (Correct answer)
Pulmonary valve (pulmonary stenosis)
Tricuspid valve (tricuspid regurgitation)

Correct answer: Mitral valve (mitral regurgitation)

Libman-Sacks endocarditis produces sterile verrucous vegetations on both surfaces of the mitral valve, causing mitral regurgitation.

Question 264: A newborn fails to pass meconium within 48 hours of birth. Rectal biopsy shows absence of ganglion cells in the submucosal and myenteric plexuses. What is the diagnosis?

Imperforate anus
Intussusception
Hirschsprung disease (Correct answer)
Meconium ileus

Correct answer: Hirschsprung disease

Hirschsprung disease is caused by failure of neural crest cell migration, resulting in an aganglionic segment of colon that cannot relax.

Question 265: A patient presents with cola-colored urine, periorbital edema, hypertension, and hematuria 2 weeks after a strep throat infection. What is the most likely diagnosis?

IgA nephropathy
Membranoproliferative GN
Henoch-Schönlein purpura nephritis
Post-streptococcal glomerulonephritis (Correct answer)

Correct answer: Post-streptococcal glomerulonephritis

Post-streptococcal GN occurs 1-3 weeks after pharyngitis, presenting with nephritic syndrome and is the classic post-infectious GN in children.

Question 266: A 45-year-old patient in the ICU develops septic shock secondary to pneumonia. Which of the following best describes the primary cardiovascular pathophysiology of this condition?

Hypovolemic shock from capillary leak syndrome
Obstructive shock due to pulmonary emboli
Cardiogenic shock due to direct myocardial suppression
Distributive shock from profound systemic vasodilation (Correct answer)

Correct answer: Distributive shock from profound systemic vasodilation

Septic shock is a classic example of distributive shock. The systemic inflammatory response to infection leads to the release of inflammatory mediators (like nitric oxide) that cause profound vasodilation and increased capillary permeability. This results in a maldistribution of blood flow, a decrease in systemic vascular resistance, and relative hypovolemia, leading to tissue hypoperfusion despite a potentially normal or high cardiac output initially.

Question 267: A 48-year-old man with a history of alcohol abuse presents with severe epigastric pain radiating to the back. His serum lipase is markedly elevated. On day two of admission, he develops a respiratory rate of 24/min, a heart rate of 110 bpm, and his BUN increases from 18 to 30 mg/dL. Which of the following is the best indicator of a severe disease course in this patient?

The etiology being alcohol-related.
The degree of lipase elevation.
The development of Systemic Inflammatory Response Syndrome (SIRS). (Correct answer)
The presence of epigastric tenderness on exam.

Correct answer: The development of Systemic Inflammatory Response Syndrome (SIRS).

The development and persistence of Systemic Inflammatory Response Syndrome (SIRS) is a key predictor of severity and mortality in acute pancreatitis, as it often precedes organ failure. The patient's tachycardia, tachypnea, and rising BUN (indicating renal dysfunction) are signs of SIRS and organ dysfunction. The absolute level of lipase does not correlate with disease severity. While alcohol is a common cause, the etiology itself is not as strong a prognostic indicator as the patient's systemic response. Epigastric tenderness is an expected finding but does not predict severity.

Question 268: First-line topical treatment for scabies in adults is:

Permethrin 5% cream (Correct answer)
Ivermectin oral
Lindane 1% lotion
Benzyl benzoate 25%

Correct answer: Permethrin 5% cream

Permethrin 5% cream applied to the entire body and left on overnight is the first-line treatment for scabies in adults and children over 2 months.

Question 269: A patient develops severe abdominal pain, fever, and watery diarrhea 5 days after completing a course of clindamycin. Colonoscopy shows yellowish plaques on the colonic mucosa. What is the treatment of choice?

Ciprofloxacin
Metronidazole or vancomycin (oral) (Correct answer)
Ampicillin-sulbactam
Rifaximin

Correct answer: Metronidazole or vancomycin (oral)

Clostridioides difficile colitis (pseudomembranous colitis) is treated with oral metronidazole for mild-moderate disease or oral vancomycin for severe disease, with fidaxomicin as an alternative.

Question 270: A 38-year-old presents with recurrent spontaneous pneumothorax. CT shows bilateral cystic lung disease. She has a history of renal angiomyolipomas. What is the most likely diagnosis?

Birt-Hogg-Dubé syndrome
Lymphangioleiomyomatosis (LAM) (Correct answer)
Langerhans cell histiocytosis
Lymphoid interstitial pneumonia

Correct answer: Lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis presents in women of childbearing age with bilateral thin-walled pulmonary cysts, spontaneous pneumothorax, and renal angiomyolipomas.

Question 271: Which finding on high-resolution CT (HRCT) chest is most characteristic of usual interstitial pneumonia (UIP) pattern?

Crazy-paving pattern
Ground-glass opacities in upper lobes
Bilateral subpleural honeycombing with traction bronchiectasis (Correct answer)
Perilymphatic nodules

Correct answer: Bilateral subpleural honeycombing with traction bronchiectasis

UIP pattern on HRCT shows bilateral, subpleural, basal-predominant honeycombing with or without traction bronchiectasis, representing the radiologic correlate of IPF.

Question 272: A 35-year-old woman with known MEN1 has recurrent peptic ulcers refractory to PPIs and fasting hypergastrinemia. What additional tumor should be sought?

Insulinoma
Glucagonoma
VIPoma
Gastrinoma (Zollinger-Ellison syndrome) (Correct answer)

Correct answer: Gastrinoma (Zollinger-Ellison syndrome)

Gastrinoma causing Zollinger-Ellison syndrome is associated with MEN1 and presents with hypergastrinemia and refractory peptic ulcers.

Question 273: A 25-year-old man with hemophilia A requires surgery. His factor VIII level is 2%. Which product replaces the deficient factor and is the treatment of choice?

Recombinant factor VIII concentrate (Correct answer)
Cryoprecipitate
Desmopressin (DDAVP)
Fresh frozen plasma

Correct answer: Recombinant factor VIII concentrate

Recombinant factor VIII concentrate is first-line for severe hemophilia A; DDAVP is only effective for mild hemophilia A (factor VIII >5%).

Question 274: Which cytokine is primarily responsible for the thrombocytosis seen in reactive (secondary) thrombocytosis following iron deficiency?

IL-11
GM-CSF
IL-6
Thrombopoietin (Correct answer)

Correct answer: Thrombopoietin

Thrombopoietin (TPO) levels rise in iron deficiency due to increased erythropoietic drive and cross-stimulation of megakaryocytes, causing reactive thrombocytosis.

Question 275: A patient with mitral stenosis develops pulmonary hypertension. Which mechanism initially elevates pulmonary arterial pressure in this condition?

Primary pulmonary arteriolar vasospasm
Passive back-transmission of elevated left atrial pressure (Correct answer)
Pulmonary vein thrombosis
Right ventricular systolic dysfunction

Correct answer: Passive back-transmission of elevated left atrial pressure

Mitral stenosis obstructs flow from left atrium to left ventricle, raising left atrial pressure that is passively transmitted backward to the pulmonary vasculature.

Question 276: A newborn presents with ambiguous genitalia, vomiting, and hyponatremia with hyperkalemia. 17-hydroxyprogesterone is markedly elevated. What enzyme is deficient?

3-beta hydroxysteroid dehydrogenase
17-alpha hydroxylase
11-beta hydroxylase
21-hydroxylase (Correct answer)

Correct answer: 21-hydroxylase

21-hydroxylase deficiency is the most common cause of congenital adrenal hyperplasia, blocking cortisol and aldosterone synthesis with excess 17-OHP accumulation.

Question 277: A 22-year-old develops fever, severe headache, petechial rash, and nuchal rigidity. CSF shows >1000 WBCs (predominantly neutrophils), low glucose, and gram-negative diplococci. Which antibiotic regimen is most appropriate?

Meropenem alone
Vancomycin + metronidazole
Ceftriaxone + dexamethasone (Correct answer)
Ampicillin + gentamicin

Correct answer: Ceftriaxone + dexamethasone

Neisseria meningitidis meningitis is treated with ceftriaxone; adjunctive dexamethasone reduces inflammation and is recommended before or with the first antibiotic dose to prevent complications.

Question 278: Which electrolyte abnormality is the primary life-threatening concern in Addisonian crisis?

Hypocalcemia and hyperphosphatemia
Hyponatremia and hyperkalemia (Correct answer)
Hypernatremia and hypokalemia
Hypomagnesemia and hypophosphatemia

Correct answer: Hyponatremia and hyperkalemia

Aldosterone deficiency in primary adrenal insufficiency leads to sodium loss and potassium retention, causing potentially fatal hyperkalemia and hyponatremia.

Question 279: A 55-year-old woman is found to have a thyroid nodule. Fine-needle aspiration cytology shows 'follicular neoplasm' (Bethesda IV). What is the recommended next step?

Observation with annual ultrasound
Radioactive iodine ablation
Repeat FNA in 6 months
Diagnostic hemithyroidectomy (lobectomy) (Correct answer)

Correct answer: Diagnostic hemithyroidectomy (lobectomy)

Bethesda IV cytology cannot distinguish follicular adenoma from carcinoma on FNA; surgical lobectomy is required for definitive histologic diagnosis.

MD Licensing Exam

The MD Licensing Exam assesses physician competency across core clinical disciplines including cardiovascular, pulmonary, renal, gastrointestinal, neurology, endocrinology, musculoskeletal, hematology, infectious disease, dermatology, and obstetrics.

280

Questions

480 min

Time Limit

75%

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