Serotonin Syndrome in Parkinson's Disease: Don't Get It Confused by a Tremor.

Serotonin syndrome (SS) is a potentially life-threatening condition caused by excessive serotonergic activity, often due to drug interactions. It classically manifests with autonomic and neuromuscular hyperactivity and by mental status changes that might include restlessness, delirium, and agitation. We present a case of a 76-year-old patient with Parkinson's disease with SS triggered by interaction between rasagiline and buspirone. He presented with altered mental status, hyperreflexia, and muscle rigidity. Due to the severity of symptoms, he was early admitted to the ICU, and his clinical condition improved after discontinuation of serotonergic agents and supportive care. In SS, a high index of suspicion is fundamental, so early treatment is implemented.