Cutaneous protothecosis is caused by the achlorophyllic algae Prototheca, typically presenting as a localized plaque in immunocompetent individuals. We report a patient with bilateral erythematous plaques and pustules on her forearms, which had initially been treated with steroids for presumed eczema. Histology showed spherical spore-like bodies with internal morula-like septation, which were positive for periodic-acid-Schiff (PAS) staining, consistent with cutaneous protothecosis. Definitive treatment with oral itraconazole resulted in resolution of the lesions.
© 2016 British Association of Dermatologists.