Phaeohyphomycosis refers to infections caused by many kinds of dark, melanin-pigmented dematiaceous fungi. It is distinguished from chromoblastomycosis and mycetoma by the absence of specific histopathologic findings.
(See also Overview of Fungal Infections.)
Phaeohyphomycosis can be caused by many species of dark, melanin-pigmented dematiaceous fungi including Bipolaris, Cladophialophora, Cladosporium, Exophiala, Fonsecaea, Phialophora, Ochronosis, Rhinocladiella, and Wangiella.
Although some species of these fungi may be true pathogens and cause phaeohyphomycosis in immunocompetent patients, pigmented fungi have been increasingly recognized as opportunists; almost all cases of widely disseminated infection occur in immunosuppressed patients. Dematiaceous fungi only rarely cause fatal infections in patients who have intact host defense mechanisms, although certain species may cause brain abscess in immunocompetent patients.
Clinical syndromes include invasive sinusitis, sometimes with bone necrosis, as well as subcutaneous nodules or abscesses, keratitis, lung masses, osteomyelitis, mycotic arthritis, endocarditis, brain abscess, and disseminated infection.
Dematiaceous fungi can frequently be discerned in tissue specimens stained with conventional hematoxylin and eosin; they appear as septate, brownish hyphae or yeast-like cells, reflecting their high melanin content. Masson-Fontana staining for melanin confirms their presence. Phaeohyphomycosis is distinguished from chromoblastomycosis and mycetoma by the absence of specific histopathologic findings such as sclerotic bodies or grains in tissue.
Culture is needed to identify the causative species.
(See also Antifungal Drugs.)
There is no standard therapy; treatment of phaeohyphomycosis depends on the clinical syndrome and status of the patient.
For subcutaneous nodules, surgery alone may be curative. Itraconazole has excellent activity and has been used the most clinically, although voriconazole and posaconazole are being increasingly used with good results. Duration of therapy varies but may range from 6 wk to > 12 mo. Amphotericin B is often ineffective.
For brain abscess, treatment should include surgical resection if possible.
For brain abscess or disseminated infections, combination therapy (eg, with 2 or 3 drugs, at least one of which is an azole) is often used, although clinical outcomes are generally poor regardless of treatment.