Case report of cutaneous protothecosis caused by Prototheca wickerhamii designated as genotype 2 and current status of human protothecosis in Japan.

An 85-year-old Japanese woman presented with infiltrative erythema and ulceration on the extensor surface of her right forearm. Direct microscopic examination demonstrated spherical and morula-like sporangia, while histopathology revealed numerous microorganisms with a mulberry-like appearance in the dermis. Staining of the microorganisms also showed mulberry-like sporangia that resembled the spokes of a wheel. The isolated yeast-like microorganism had been identified as Prototheca wickerhamii genotype 2 in another independent study on the basis of its morphological, biochemical and genetic analysis. This case of protothecosis was recorded in Kyushu, Japan, and oral treatment with itraconazole 200 mg/day for 2 months was effective. Herein, we also summarize and analyze 39 cases of human protothecosis reported in Japan since the first record in 1983.