Phaeohyphomycosis
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.
Pigmented fungi have been increasingly recognized as opportunists, causing
phaeohyphomycosis in immunocompetent and immunosuppressed patients.
Phaeohyphomycosis can be caused by many species of dark, melanin-pigmented
dematiaceous fungi including Bipolaris, Cladophialophora, Cladosporium,
Exophiala, Fonsecaea, Phialophora, Ochronosis, Rhinocladiella, and Wangiella.
Dematiaceous fungi only rarely cause fatal infections in patients who have intact host
defense mechanisms, although they 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.
Diagnosis
Examination using Masson-Fontana staining
Culture to identify causative species
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.
Treatment
There is no standard therapy; treatment 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.
Combination therapy (eg, with 2 or 3 drugs, at least one of which is an azole) for
brain abscess and disseminated infections is often used, although clinical outcomes
are generally poor regardless of treatment.