Two Cases of phaeohyphomycosis on the fingers in immunocompromised patients

Abstract

Phaeohyphomycosis is a mycotic infection caused by chromomycotic fungi that produce hyphae in tissues.　Phaeohyphomycosis is commonly associated with immunocompromised hosts. Here, we report two cases of phaeohyphomycosis on the fingers in immunocompromised hosts, one of which was diagnosed by direct microscopy. Case 1 was of an 87-year-old male with lung cancer (stage IVB) under palliative treatment who developed a subcutaneous solitary abscess on his left ring finger. He received a scratch wound on his left hand three months prior. A direct microscopic examination of the pus revealed a lot of hyphae. Mycological cultures after 18 days of incubation revealed filamentous colonies. Slide culture technique for fungi showed hyphae with phialides that ended in a wide-angled collarettes. DNA sequence analysis using the cultured fungus identified Pleurostomophora richardsiae. Case 2 was of an 80-year-old male with poorly controlled type 2 diabetes mellitus who developed a small nodule on his right thumb two months prior. Mycological cultures after 21 days of incubation revealed black filamentous colonies. DNA sequence analysis using the cultured fungus showed high homology with Exophiala xenobiotica. In both cases, treatment with oral terbinafine was effective. Recently, the number of patients with phaeohyphomycosis has increased; therefore, it is important to consider this disease in differential diagnosis cases, particularly for immunocompromised patients with antibacterial drug-resistant abscess on the fingers. A direct microscopic examination of the pus may be useful in making a rapid diagnosis, which is conducive to phaeophyphomycosis.