Medical Knowledge 10 Flashcards

A 58-year-old patient on long-term amiodarone therapy presents with progressive dyspnea, a dry cough, and bilateral interstitial infiltrates on chest X-ray. Pulmonary function tests reveal a restrictive pattern with reduced DLCO. Which mechanism best explains this complication?

Answer: Direct oxidative injury to type II pneumocytes mediated by reactive oxygen species from amiodarone metabolites

Amiodarone pulmonary toxicity occurs in up to 5% of long-term users and is primarily caused by direct cytotoxic injury. Amiodarone and its active metabolite desethylamiodarone accumulate in lung tissue and generate reactive oxygen species that damage type II pneumocytes. This leads to a phospholipidosis pattern (foamy macrophages) and organizing pneumonia or nonspecific interstitial pneumonia on biopsy. The reduced DLCO reflects impaired gas exchange due to this fibrotic process, not bronchospasm or immune-complex deposition.

A 34-year-old woman presents with recurrent episodes of severe hypertension, headache, and diaphoresis lasting 15–20 minutes. Her 24-hour urine catecholamines are borderline elevated. An MRI of the abdomen reveals a 2.5 cm adrenal mass. Genetic testing is most likely to identify a mutation in which gene, given that she also has a family history of cerebellar hemangioblastomas?

Answer: VHL tumor suppressor gene

Von Hippel-Lindau (VHL) disease is caused by mutations in the VHL tumor suppressor gene and is associated with pheochromocytoma, cerebellar and retinal hemangioblastomas, clear cell renal carcinoma, and pancreatic cysts. The combination of a catecholamine-secreting adrenal tumor with cerebellar hemangioblastomas in a young woman with family history is the classic VHL triad. RET mutations cause MEN2 (associated with medullary thyroid carcinoma), SDHB mutations cause hereditary paraganglioma syndrome, and NF1 mutations cause neurofibromatosis type 1.

During a busy emergency shift, a physician administers a medication to an unconscious patient who arrives without identification. The family arrives an hour later and objects to the treatment on religious grounds, stating the patient had previously expressed similar views. Under DHA ethical and legal framework, what is the most accurate assessment of the physician's initial action?

Answer: The action was justified under the doctrine of implied consent for emergency life-saving treatment in the absence of a known advance directive

Under the DHA Health Regulation Law and internationally recognized bioethical principles, implied consent applies in genuine emergencies where a patient is incapacitated, the condition is life-threatening, and no advance directive or legal guardian is immediately available. The physician acted appropriately. However, once family members arrive and communicate the patient's previously expressed wishes, the care team must reassess and involve the ethics committee if conflict persists — they cannot simply override the family without due process, but the initial treatment was legally and ethically defensible.

A 45-year-old male with type 2 diabetes presents with a non-healing plantar ulcer. Wound culture grows Pseudomonas aeruginosa. He is started on piperacillin-tazobactam. On day 3, his serum creatinine rises from 0.9 to 2.4 mg/dL. Which mechanism most accurately explains the nephrotoxicity seen with extended-infusion beta-lactam therapy in this context?

Answer: Acute interstitial nephritis mediated by a T-cell hypersensitivity reaction to the beta-lactam ring

Beta-lactam antibiotics, including piperacillin-tazobactam, are a leading cause of drug-induced acute interstitial nephritis (AIN). The mechanism is a delayed T-cell–mediated (type IV) hypersensitivity reaction targeting tubular cells. AIN classically presents with an abrupt rise in creatinine 3–10 days after drug initiation, and may be accompanied by eosinophilia, eosinophiluria, or sterile pyuria, though the 'classic triad' (rash, fever, eosinophilia) is absent in most cases. Treatment involves drug cessation and, in severe cases, corticosteroids. Crystal nephropathy is associated with sulfonamides and certain antivirals, not beta-lactams.

A 28-year-old woman in her 32nd week of gestation is brought to the ED with a generalized tonic-clonic seizure. Her blood pressure is 168/112 mmHg, and urinalysis shows 3+ proteinuria. She is given IV magnesium sulfate. Thirty minutes later, she develops bradypnea (6 breaths/min), absent deep tendon reflexes, and confusion. What is the most appropriate immediate intervention?

Answer: Administer IV calcium gluconate to reverse magnesium toxicity

The clinical picture — absent deep tendon reflexes, bradypnea, and altered consciousness after magnesium sulfate infusion — is classic magnesium toxicity. Loss of patellar reflexes occurs at serum Mg2+ ~7–10 mEq/L, respiratory depression at ~10–13 mEq/L, and cardiac arrest at >15 mEq/L. Calcium gluconate (1 g IV over 3 minutes) is the specific antidote: calcium directly antagonizes the neuromuscular and cardiovascular effects of magnesium. The magnesium infusion must also be stopped immediately. Increasing fluids is too slow, diazepam would worsen respiratory depression, and cesarean section does not address the acute toxidrome.

A 62-year-old man with a 40-pack-year smoking history undergoes bronchoscopy for a central lung mass. Biopsy shows small, round, blue cells with nuclear molding, scant cytoplasm, and a high mitotic index. Immunohistochemistry is positive for synaptophysin, chromogranin A, and TTF-1, with a Ki-67 index of 90%. He presents two weeks later with hyponatremia (Na+ 122 mEq/L), elevated urine osmolality (480 mOsm/kg), and low serum osmolality. Which paraneoplastic mechanism is responsible?

Answer: Ectopic ADH (arginine vasopressin) secretion causing dilutional hyponatremia

The biopsy findings — small blue cells, nuclear molding, neuroendocrine markers (synaptophysin, chromogranin), TTF-1 positivity, and Ki-67 ~90% — are diagnostic of small cell lung carcinoma (SCLC). The electrolyte picture (low serum Na+, elevated urine osmolality, normal volume status) is classic SIADH (syndrome of inappropriate antidiuretic hormone secretion), the most common paraneoplastic syndrome in SCLC. The tumor cells secrete ectopic ADH, which causes excessive free water reabsorption in collecting ducts, diluting serum sodium. Ectopic ACTH causes Cushing's syndrome (hypokalemia, hypertension), not hyponatremia. Cerebral salt wasting features volume depletion, distinguishing it from SIADH.