Neurological Insights: Transient Unilateral Relative Afferent Pupillary Defect in the Context of Serotonin Syndrome

The pupillary reflex is a complex physiological response involving both the eye and associated neural pathways. Relative afferent pupillary defects (RAPDs) can present due to various underlying pathologies, yet their occurrence in serotonin syndrome has been rarely documented. This report details the case of a 21-year-old non-binary individual with a history of bipolar disorder who presented to the emergency department following a polypharmacy overdose, including significant ingestion of sertraline, aripiprazole, and buspirone. The patient exhibited symptoms consistent with serotonin syndrome, prompting immediate intervention. Notably, a unilateral afferent pupillary defect was identified alongside mydriasis, hyperreflexia, and inducible clonus. This case highlights the significance of clarifying the connection between RAPD and serotonin syndrome to improve clinical recognition and understanding of how excess serotonin affects neurological and ophthalmic processes.