Serotonin syndrome presenting as febrile encephalopathy with CSF pleocytosis: a report of three cases.

Serotonin syndrome (SS) is an iatrogenic, drug-induced clinical syndrome caused by serotoninergic hyperstimulation. SS may have protean manifestations and can mimic a variety of medical conditions. Herein, we describe three cases of febrile encephalopathy who were on serotonergic agents. All three cases fulfilled Hunter's criteria for SS and responded to the removal of the offending agents and the administration of cyproheptadine. All three patients had abnormal cerebrospinal fluid (CSF) examinations (pleocytosis in three patients and increased protein in two patients) which returned to normal with therapy. We suggest that SS presenting as febrile encephalopathy may have transient CSF abnormalities. Severe SS is a medical emergency. Therefore, a trial of cyproheptadine can be given in patients fulfilling the SS criteria even in the presence of CSF abnormalities. In parallel, the patients should be investigated for other causes of febrile encephalopathy and CSF pleocytosis.