Cutaneous protothecosis is a rare indolent condition occurring mostly in immunocompromised patient, caused by members of the genus Prototheca. These organisms are considered to be achlorophyllic algae which are ubiquitous in nature. Risk factors include prolonged steroid use, acquired immunodeficiency syndrome, diabetes mellitus and underlying malignancy. Microscopic findings on tissue biopsy and culture of the skin tissue are required for diagnosis. The incidence of protothecosis is likely to increase, given the ever increasing number of immunocompromised patients.
The case is that of a 64-year-old male who presented with 1 week history of superficial ulcers with pinpoint purpura on his fingertips. He had a background history of insulin dependent diabetes mellitus and dermatomyositis, and was on regular prednisolone therapy. Histopathology of the cutaneous biopsy revealed moderate acute inflammation within the dermis and subcutaneous fat. Numerous morula-like structures were apparent in the dermis, singly and in clusters. Characteristic septations were seen with formation of endospores. Periodic acid-Schiff and silver stains highlighted the organisms. With microbiological correlation, diagnosis of protothecosis was made.
(C) 2014 Royal College of Pathologists of Australasia