Cutaneous protothecosis.

Abstract

A 63‐year‐old Korean woman presented with erythematous plaques on her right forearm. The lesion had developed 4 months previously as pruritic papules and scaly patches, and grew slowly coalescing to eczematous plaques. Examination showed thick scaly erythematous plaques with multiple erosions and minute pustules over the right forearm (Fig. 1). Her past history included hypertension and chronic arthritis of her knees requiring intermittent corticosteroid therapy over a period of 15 years. Routine laboratory evaluations (complete blood count, erythrocyte sedimentation rate (ESR), urinalysis, renal and liver function) and chest X‐ray studies were negative or within normal limits. The biopsy specimens of the plaque revealed mild acanthosis and mixed inflammatory infiltrates with some round spores in the dermis, which showed multiple morula‐like sporangia containing many endospores on periodic acid‐Schiff (PAS) and Gomori's methenamine silver (GMS) staining (Fig. 2). Scraping of the lesion with potassium hydroxyde examination showed no specific findings, but the tissue culture revealed creamy yeast‐like colonies on Sabouraud dextrose agar (SDA) in room temperature within 48 h, and the colonies showed characteristic sporangia with morula‐like appearance on lactophenol cotton blue staining. The biochemical evaluation using a Yeast biochemical card (Vitec®, bioMérieux, France) identified the organisms as Prototheca wickerhamii, which assimilated galactose, trehalose, glycerol and glucose on the kit. Oral itraconazole (200 mg/day) for 8 weeks resulted in complete healing with remaining mild pigmentation, and there was no evidence of recurrence over the following 12 months.Scaly erythematous and eczematous plaque on the right forearmimageBiopsy specimen showing mixed inflammatory cell infiltrates in the dermis (H&E, × 200) and multiple morula‐like sporangia on Gomori's methenamine silver staining (inset, × 200)image