Which of the following is NOT a symptom of serotonin syndrome?

• A. Rash
• B. Hyperreflexia
• C. Fever
• D. Myoclonus

Answer: (A)

Excess serotonin in the central nervous system drives a mix of autonomic, cognitive, and neuromuscular symptoms. Typical neuromuscular signs include hyperreflexia and clonus, along with tremor or myoclonus, and autonomic features such as fever, tachycardia, hypertension, and sweating. Rash does not result from serotonergic toxicity and is not part of the serotonin syndrome picture. If a patient on serotonergic medications develops fever and neuromuscular excitement with hyperreflexia or clonus, those findings point toward serotonin syndrome rather than a skin-related reaction. The absence of a rash helps distinguish it from dermatologic or allergic processes that can present with skin involvement. In short, fever, hyperreflexia, and myoclonus are characteristic, while a rash is not.