A case of cutaneous protothecosis

Protothecosis is a rare skin infection caused by pathogenic algae of the genus Prototheca, especially Prototheca wickerhamii. It is widely distributed throughout the natural world in tree, river, lake, sewage, soil, marsh, household waste, etc. A 79-year-old woman presented with ill-defined edematous and erythematous patches with various sized and shaped deep ulcers on both dorsal hands and left distal forearm for 1 month. The left forearm was initially injured by scratching due to pruritus and insidiously aggravated. Biopsy specimen revealed the characteristic morula-like sporangias containing multiple endospores in the dermis. The GMS and D-PAS stains highlighted the characteristic spores showing multiple internal septations and some unicellular endospore. P. wickerhamii was isolated in culture and identified by biochemical studies. Oral itraconazole 200 mg/day administration for 7 weeks resulted in marked improvement of the skin lesion.