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Serotonin syndrome — USMLE Step 2 CK MCQ

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ModeratePsychiatrySerotonin syndromeUSMLE Step 2 CK

A 32-year-old Asian American man comes to the urgent care clinic because of changes in mood, behavior, or thinking. History and focused examination are notable for hyperthermia, agitation, clonus, hyperreflexia, and recent serotonergic drug use. Temperature is 98.6°F (37.0°C), blood pressure is 126/78 mmHg, pulse is 84/min, respirations are 16/min, and oxygen saturation is 98% on room air. Physical examination confirms the key finding and shows no unrelated abnormality that would better explain the presentation. There is no evidence of intoxication, delirium, or a primary neurologic disorder unless described in the vignette. Which of the following is the most likely cause of this patient's condition?

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Correct answer: C — Excess serotonergic activity at central and peripheral receptors

The vignette describes Serotonin syndrome, supported by hyperthermia, agitation, clonus, hyperreflexia, and recent serotonergic drug use. Excess serotonergic activity at central and peripheral receptors is the single best answer because it matches the diagnostic or management priority in this clinical setting. The other choices are plausible alternatives in related presentations, but they do not best fit the timing, findings, and guideline-directed approach described here.

Reference: https://www.ncbi.nlm.nih.gov/books/#stage-9-order-37