USMLE Step 1 Sample Questions
6 practice questions with complete answer explanations.
Sample Questions
A 55-year-old man presents with chest pain radiating to the left arm, diaphoresis, and nausea. ECG shows ST elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?
Explanation
ST elevation in II, III, aVF indicates inferior MI, typically from right coronary artery occlusion (in ~80% of cases).
A 23-year-old woman presents with fatigue, jaundice, and dark urine after eating fava beans. Lab shows normocytic anemia, elevated LDH, and bite cells on peripheral smear. The deficient enzyme is most likely:
Explanation
G6PD deficiency → inability to regenerate NADPH → Heinz bodies → hemolysis triggered by oxidative stress (fava beans, sulfa drugs, infection). Bite cells are classic.
A patient presents with a moon face, truncal obesity, purple striae, and hypertension. 24-hour urinary free cortisol is elevated. Low-dose dexamethasone fails to suppress cortisol but high-dose does. Which is the most likely diagnosis?
Explanation
Cushing disease: pituitary tumor producing ACTH — partial feedback suppression at high-dose dexamethasone distinguishes it from adrenal tumors (no suppression) and ectopic ACTH (usually no suppression either).
A 6-year-old presents with a rash that started on the cheeks ('slapped cheek'), followed by a lacy reticular rash on the trunk and arms. Which virus is responsible?
Explanation
Parvovirus B19 → erythema infectiosum (fifth disease) with classic slapped-cheek rash followed by lacy body rash.
A drug inhibits bacterial 30S ribosomal subunit and causes tooth discoloration in children. Which drug is it?
Explanation
Tetracyclines (doxycycline) bind 30S and cause tooth discoloration in children under 8 — hence avoided in pregnancy and young kids.
A 45-year-old alcoholic presents with confusion, ataxia, and ophthalmoplegia. Which vitamin is most likely deficient?
Explanation
Wernicke encephalopathy: the classic triad of confusion, ataxia, ophthalmoplegia in a malnourished patient is thiamine (B1) deficiency. Treat before glucose.
Test-Taking Tips
- 1.Start with a dedicated Qbank like UWorld — it's the gold standard.
- 2.Read First Aid 2–3 times, annotating with Qbank insights.
- 3.Do practice questions daily, even during coursework.
- 4.Focus on high-yield topics: pathology, pharmacology, physiology, microbiology.
- 5.Take NBME practice exams every 1–2 weeks in dedicated prep.
- 6.Sleep 7–8 hours — memory consolidation matters more than cramming.
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