Abstract: LIU Ze-hu, XIA Xiu-jiao, ZHONG Yan, SANG Bo, LV Wen-wen, WANG Mei, SHEN Hong, XU Ai-e. Department of Dermatology, Third People′s Hospital of Hangzhou, Hangzhou 310009, China Corresponding author: SHEN Hong, Email: shenhongsh@medmail.com.cn 【Abstract】 A 68-year-old woman presented with a four-year history of rheumatoid arthritis and a four-month history of erythematous plaque on the left forearm. Dermatological examination revealed a dark erythematous, ill-defined plaque measuring 5 cm × 10 cm over the left dorsal hand, wrist, and forearm, with purpura and a small amount of purulent discharge. Direct microscopic examination of the pus in 10% potassium hydroxide showed pale brown, branched and septate hyphae. Culture of pus and lesional tissue grew dark gray, velvety, confined colony on Sabouraud dextrose agar. Slide cultures on potato dextrose agar resulted in the formation of dark septate hyphae, but no spores were observed. Histopathological examination of the lesional tissue revealed infectious granuloma, and periodic acid-Schiff staining showed violet to red yeasts and pseudohyphae. Sequencing analysis of the internal transcribed spacer （ITS） region revealed a 99% consistence between the clinical isolate and reference strain of Microsphaeropsis arundinis. Based on the above findings, the patient was diagnosed with subcutaneous phaeohyphomycosis caused by M. arundinis. She was given itraconazole 400 mg once daily orally as well as thermotherapy. Four months later, the lesion completely resolved. No recurrence was observed during one-year follow-up. 【Key words】 Phaeohyphomycosis; Coelomycetes; Microsphaeropsis arundinis; Arthritis, rheumatoid

Key words: Microsphaeropsis arundinis