USMLE Step 1 practice test

A 58-year-old man with hypertension is started on a new medication and three weeks later develops a persistent dry cough without wheezing or sputum. His cough resolves after the drug is discontinued. The cough is most likely caused by accumulation of which substance?

A 65-year-old man with a long smoking history develops a central lung mass. Biopsy shows keratin pearls and intercellular bridges. He is also found to have an elevated serum calcium level with low parathyroid hormone. Which paraneoplastic mechanism best explains the hypercalcemia?

A 6-month-old infant develops irritability, poor feeding, and an enlarged liver after fruit juice is introduced into the diet. Laboratory studies show hypoglycemia after fructose ingestion. The condition is caused by a deficiency of which enzyme?

A healthy person quickly stands up from a lying position. Baroreceptors in the carotid sinus detect a transient drop in blood pressure. Which immediate compensatory response is expected?

A 55-year-old man undergoes surgery in the posterior triangle of the neck and afterward cannot shrug the shoulder or fully turn the head against resistance. Injury to which cranial nerve best explains these findings?

A 45-year-old woman with poorly controlled diabetes presents with proteinuria. A renal biopsy shows nodular accumulations of pink material in the glomerular mesangium. These nodules are characteristic of which finding?

A 70-year-old man with atrial fibrillation and heart failure is taking digoxin. He develops nausea, blurred yellow-tinged vision, and a new arrhythmia. Which electrolyte abnormality most predisposes a patient to digoxin toxicity?

A 30-year-old man develops watery diarrhea after a hiking trip during which he drank from a freshwater stream. Stool examination reveals motile, pear-shaped trophozoites with two nuclei. Which organism is the most likely cause?

A study reports that a new screening test for a disease has high sensitivity but low specificity. For a patient who tests positive on this screening test, which statement is most accurate?

A 24-year-old woman presents with a malar rash, joint pain, fatigue, and proteinuria. Laboratory testing shows positive antinuclear antibodies and high-titer anti-double-stranded DNA antibodies. Which antibody is most specific for this diagnosis?

A patient hyperventilates due to anxiety. Arterial blood gas analysis shows a high pH, low carbon dioxide, and a slightly low bicarbonate. Which acid-base disorder does this represent?

A 4-year-old child has recurrent infections, a history of bleeding tendencies, and partial albinism. A peripheral blood smear shows giant granules in neutrophils. This disorder is caused by a defect in which cellular process?

A 62-year-old woman is started on a statin for hyperlipidemia. Statins lower cholesterol primarily by inhibiting which enzyme in the cholesterol synthesis pathway?

A 5-year-old unvaccinated child develops a severe sore throat with a gray, adherent pseudomembrane over the tonsils and pharynx. The toxin responsible for the disease acts by which mechanism?

A patient sustains a midshaft fracture of the humerus and afterward cannot extend the wrist, resulting in wrist drop. Which nerve was most likely injured?

A 68-year-old man has a screening colonoscopy that reveals a polyp. Histology shows dysplastic glandular epithelium without invasion through the basement membrane. Which term best describes this lesion?

A patient develops diabetes insipidus after head trauma. The kidneys produce large volumes of dilute urine because of a deficiency or reduced action of which hormone?

A patient with an opioid overdose presents with respiratory depression and pinpoint pupils. Which medication should be administered as an antidote, and what is its mechanism?

A 30-year-old patient newly diagnosed with a serious illness insists there has been a laboratory mistake and that the diagnosis cannot be correct, despite clear evidence. According to the Kubler-Ross model, which stage of grief does this represent?