Dermatology Online Journal

Protothecosis is a rare but emerging infectious disease, caused by algae from the genus Prototheca. It presents predominantly as cutaneous lesions and poses a diagnostic challenge owing to its diverse clinical presentation. Typically, it occurs in exposed areas of the skin, associated with trauma. Diagnosis relies mainly on histopathology and culture. This article presents an elderly diabetic woman with cutaneous protothecosis from Rio de Janeiro, Brazil. We emphasize clinical features, histopathology, and successful treatment with itraconazole, along with a brief review of the 12 previously reported cases from Brazil.