Abstract: Objective To report a case of cutaneous mycosis caused by Arthrinium phaeospermum. Methods A 25-year-old male patient presented an infiltrative plaque on the left buttock. The lesion appeared 20 years ago after intramuscular injection, which was a painful swelling at the beginning, then suppurated, and slowly developed into an infiltrative plaque. Last year the lesion developed very fast with intense pain. Dermatological examination showed a verrucous, granulomatous lesion on the left buttock with tenderness and bad smell. Several ulcerations and erosions were observed on the surface of the lesion, and purulent discharge overflowed when squeezed. There was a light brown atrophic patch in the center of the lesion with elevated border and black crusts on it. Specimens were taken from the skin lesion of the patient. Then, microscopic examination, culture and histopathological examination were performed to identify the pathogen. The histopathologic features were reproduced through animal pathogenicity study with a rabbit model. The antifungal susceptibility test was done also. Results The fungal hyphae were not found on direct microscopy and histopathological examination. The strains of the fungus on the mycological culture medium were found just the same for five times, where the hyaline, thread-like conidiophores grew from gourd-form mother cell and bore lateral conidia. The feature of conidia was lenticular in shape, dark brown, with a germ-slit in the middle. Hyphae and swollen cells resembling chlamydospores were observed in the scrapings of skin lesion of the experimental infection of the rabbit. The MIC values of 5 antifungals were as follows: fluconazole >64 μg/mL, itraconazole>64 μg/mL, turbinafine 0.125 μg/mL, ketoconazole 4.0 μg/mL, and miconazole 8.0 μg/mL. Conclusion Based on the morphology of colony on SDA and the characteristic structures under the microscope, this is a case of subcutaneous infection caused by Arthrinium phaeospermum.

Key words: Arthrinium phaeospermum, Dermatomycoses, Animal testing alternatives