Exophiala

Background

• Genus of dematiaceous filamentous fungi
• Exophiala dermatitidis is the most clinically relevant "black yeast"

Clinical Manifestations

• Causes cutaneous and subcutaneous infection most commonly, including phaeohyphomycosis, chromoblastomycosis, eye infections, and nail infections
• Also pneumonia, brain abscess, disseminated disease (in elderly and immunosuppressed patients including AIDS and chemotherapy)
• Exophiala dermatitidis is neurotropic, with high mortality
• Known to colonize cystic fibrosis patients (3-20%)

Diagnosis

• On histology of cutaneous infection, shows epidermal hyperkeratosis, hyperplasia, acanthosis, pseudoepitheliomatous and intraepidermal pustules
• Culture
  • Colony: yeast-like, black, and mucoid
  • Microscopy
    • Can have pigmented fungal elements within or adjoining multinucleate giant cells
    • Yeast form is budding and black, while filamentous form is septate and pigmented.

Management

• Itraconazole or oral terbinafine, alone or in combination
• Amphotericin B is also commonly used, and voriconazole also likely works