Which features are typical of serotonin syndrome?

• A. Autonomic instability, hyperreflexia, clonus
• B. Hypothermia and miosis
• C. Seizures only
• D. Insomnia only

Answer: (A)

Serotonin syndrome arises from excessive serotonergic activity in the central nervous system and periphery, producing a distinctive mix of autonomic, cognitive, and neuromuscular signs. The best choice reflects autonomic instability—things like tachycardia, hypertension, hyperthermia, and diaphoresis—together with neuromuscular hyperreactivity, notably hyperreflexia and inducible clonus. This combination is classic for serotonin syndrome and helps distinguish it from other conditions. The other options don’t fit: hypothermia with miosis isn’t typical and points away from this syndrome; seizures can occur but are not the defining cluster; insomnia alone is too nonspecific to describe the syndrome’s profile.