MD Medical Doctor General 5 — Questions and Answers
Question 1: A 40-year-old man presents with symmetric proximal muscle weakness, elevated CK, and a heliotrope rash around the eyes. What is the most likely diagnosis?
- Fibromyalgia
- Polymyositis
- Dermatomyositis (Correct answer)
- Inclusion body myositis
Correct answer: Dermatomyositis
Dermatomyositis presents with proximal muscle weakness, elevated CK, and characteristic skin findings including heliotrope rash and Gottron's papules.
Question 2: Which mechanism is responsible for the antiplatelet effect of aspirin?
- Reversible inhibition of ADP receptors on platelets
- Irreversible inhibition of cyclooxygenase, blocking thromboxane A2 synthesis (Correct answer)
- Inhibition of glycoprotein IIb/IIIa receptor
- Enhancement of prostacyclin synthesis in endothelium
Correct answer: Irreversible inhibition of cyclooxygenase, blocking thromboxane A2 synthesis
Aspirin irreversibly acetylates COX-1 in platelets, permanently blocking thromboxane A2 synthesis for the platelet's lifespan (~10 days).
Question 3: A 55-year-old woman with known cirrhosis presents with confusion, asterixis, and elevated ammonia. What precipitant should be ruled out first?
- Hyponatremia
- Gastrointestinal bleeding (Correct answer)
- Hyperglycemia
- Pulmonary embolism
Correct answer: Gastrointestinal bleeding
GI bleeding is a common precipitant of hepatic encephalopathy because blood protein in the gut is metabolized by bacteria to ammonia, worsening encephalopathy.
Question 4: A 22-year-old with sickle cell disease presents with sudden onset severe pain in the long bones. Temperature is 38.5°C. The most common organism causing osteomyelitis in sickle cell patients is:
- Staphylococcus aureus
- Salmonella species (Correct answer)
- Streptococcus pneumoniae
- E. coli
Correct answer: Salmonella species
While S. aureus is the most common cause of osteomyelitis in the general population, Salmonella is disproportionately common in sickle cell disease due to functional asplenia.
Question 5: A patient with COPD exacerbation on supplemental oxygen develops increasing somnolence. ABG shows pH 7.30, PaCO2 65 mmHg, PaO2 75 mmHg. What is the most likely cause of somnolence?
- Hypoxic respiratory drive abolished by oxygen
- Hypercapnic narcosis from CO2 retention (Correct answer)
- Medication side effect
- Cerebral edema from hypoxia
Correct answer: Hypercapnic narcosis from CO2 retention
In COPD patients with chronic hypercapnia, elevated oxygen delivery removes the hypoxic drive, leading to hypoventilation and CO2 narcosis.
Question 6: Which of the following is the most appropriate screening test for colorectal cancer in an average-risk 45-year-old?
- Annual fecal occult blood test alone
- Colonoscopy every 10 years (Correct answer)
- Flexible sigmoidoscopy every 5 years
- CT colonography every 3 years
Correct answer: Colonoscopy every 10 years
Colonoscopy every 10 years beginning at age 45 is the preferred screening method for colorectal cancer in average-risk individuals per current US guidelines.
Question 7: A 65-year-old with atrial fibrillation has a CHA2DS2-VASc score of 3. Which therapy is most appropriate to reduce stroke risk?
- Aspirin alone
- Aspirin plus clopidogrel
- Oral anticoagulation (warfarin or DOAC) (Correct answer)
- Rate control without anticoagulation
Correct answer: Oral anticoagulation (warfarin or DOAC)
A CHA2DS2-VASc score ≥2 in males warrants oral anticoagulation (preferably a DOAC); aspirin alone is inadequate for stroke prevention in AF.
MD Medical Doctor General 5
A 40-year-old man presents with symmetric proximal muscle weakness, elevated CK, and a heliotrope rash around the eyes.
What is the most likely diagnosis?