Dematiaceous

Dematiaceous describes pigmented fungi whose cells contain dark melanin, yielding brown to black colonies in culture and darkly pigmented hyphae and spores in tissue. The term is descriptive, not taxonomic; dematiaceous fungi comprise diverse lineages across multiple orders, unified by the presence of melanin in their cell walls rather than a single common ancestor.

They are widespread in the environment, typically found in soil, plant debris, wood, and other decaying vegetation. In clinical settings, dematiaceous fungi are notable as opportunistic pathogens capable of causing a spectrum of infections, from superficial cutaneous lesions to more invasive disease. Melanin production is thought to provide protection against environmental stresses and may contribute to virulence in some species.

In human disease, dematiaceous fungi cause phaeohyphomycosis (involving pigmented hyphae in tissue) and chromoblastomycosis (characterized histologically by sclerotic bodies). They can also cause eumycetoma. Infections are more common in individuals with impaired immunity or after trauma to the skin or nails, and they can be chronic. Diagnosis relies on culture, microscopic examination of clinical specimens, and histopathology, often supported by molecular methods. Treatment typically involves antifungal therapy, with agents such as itraconazole or voriconazole, and may include surgical excision or debridement depending on the site and severity.

Examples of dematiaceous genera include Alternaria, Cladosporium, Exophiala, Fonsecaea, Curvularia, and Bipolaris.