Phaeohyphomycosis caused by Diaporthe phaseolorum in an immunocompetent patient in Thailand: a case report

Phaeohyphomycosis is caused by a large, heterogeneous group of darkly pigmented fungi. It is an infrequent infection in humans. However, the prevalence has been increasing in recent years especially in immunocompromised patients. Diaporthe phaseolorum is a common black fungal pathogen of plants, which rarely causes human infection. We report the first case of cutaneous infection caused by Diaporthe phaseolorum in an immunocompetent host and the first in Asia. Although, the review of the literature revealed two previous cases of cutaneous infection caused by this organism, both of them were in immunocompromised hosts. A slow-growing asymptomatic nodule was the major clinical feature. Histopathological examination showed granulomatous inflammation and pigmented septate hyphae and yeast-like cells. The fungal isolation was identified by morphological characteristics and DNA sequencing. The lesion was resolved after complete surgical excision and oral fluconazole for two months. This report highlights the potential role of Diaporthe phaseolorum as an emerging cause of infection in immunocompetent patients.