A case of cutaneous protothecosis in a polyarteritis nodosa patient and review of cases reported in Japan.

A 76-year-old woman farmer with a 20-year history of oral steroid treatment for polyarteritis nodosa, noted a rash consisting of numerous small papules on the dorsum of her right hand in February 2007. The rash worsened over time, and in April 2008 red papules and pustules as big as grains of rice fused to form plaques extending up her arm from the dorsum of the right hand to the extensor surface of the forearm. The plaques were accompanied by erosions, ulcers, and crusts. Skin biopsy specimens from the dorsum of the right hand showed a dense cell infiltration in the upper to middle layer of the dermis, with numerous morula-like microorganisms within the cells. Cultures of the specimens on Sabouraud dextrose agar produced creamy, yeast-like colonies. The colonies produced sporangia, with cells of varying sizes arranged in the pattern of a spoked-wheel. The microorganisms were identified as Prototheca wickerhamii on the basis of their morphological characteristics, sugar assimilation patterns, and molecular biological techniques. Treatment with amphotericin B was planned, but the patient died from respiratory failure before initiating treatment. We review the characteristics of the cutaneous protothecosis cases reported to date in Japan.