A case of phaeohyphomycosis caused by Exophiala oligosperma successfully treated with local hyperthermia

A 58-year-old Japanese woman who was engaged in dairy farming presented with multiple subcutaneous nodules and abscesses on the dorsum of her left hand from 5 months ago. These had been unsuccessfully treated with oral itraconazole. The patient had a history of Sjögren syndrome and diabetes mellitus, for which she had been taking oral prednisolone for 10 years. Direct microscopy of a pus sample treated with potassium hydroxide (KOH) showed brownish-red branching hyphae. In fungal culture, black colonies covered with gray-white villi were formed. Slide culture showed conidiogenesis from an annellide. The fungal strain was identified as Exophialia oligosperma by molecular biological techniques. Histopathological examination revealed abscesses and surrounding granulomatous infiltration in the dermis and subcutis, and hyphae in the granulomatous infiltration in the outer area. However, no eumycotic granules were observed. The diagnosis was phaeohyphomycosis caused by E. oligosperma. Since the previous treatment with itraconazole had not been effective, we performed daily hyperthermia using a disposable body warmer and drainage of the pus, which ceased after 3 weeks. After approximately 4 months, the skin eruptions became scarred. To the best of our knowledge, this is the second case of phaeohyphomycosis caused by E. oligosperma reported in Japan which was successfully treated with hyperthermia.