Cutaneous Small Vessel Vasculitis Secondary to Clozapine Use in a 22-Year-Old Man With Treatment-Resistant Schizophrenia.

Clozapine is the most effective drug for treatment-resistant schizophrenia (TRS) but is associated with several adverse effects, including rare immune-mediated reactions. Cutaneous small vessel vasculitis (CSVV), also known as leukocytoclastic vasculitis, is an uncommon complication that typically presents as palpable purpura involving dependent areas of the body. We describe a case of a 22-year-old male patient with TRS who developed a painful, non-blanching purpuric, papular rash over both lower limbs two weeks after initiation and dose escalation of clozapine. Laboratory evaluation showed mild leukocytosis with eosinophilia, while renal, hepatic, infectious, and immunological investigations were normal, and there was no evidence of systemic involvement. In view of the clear temporal association with clozapine initiation and absence of alternative causes, a diagnosis of drug-induced CSVV was made. Clozapine was discontinued, and the patient was transitioned to quetiapine for ongoing psychiatric management. The vasculitic lesions were managed with systemic corticosteroids, antihistamines, pentoxifylline, and supportive measures, resulting in marked improvement within two weeks and complete resolution over six weeks without recurrence. Causality assessment using the Naranjo adverse drug reaction probability scale gave a score of 6, suggestive of a probable association with clozapine. Rechallenge was avoided due to the risk of recurrence. This case emphasizes the need for clinicians to recognize rare immune-mediated cutaneous reactions associated with clozapine. Early recognition and prompt discontinuation of the offending agent are essential to prevent progression and ensure favorable outcomes.