Chromoblastomycosis is a cutaneous infection caused by dematiaceous (pigmented) fungi. Symptoms are ulcerating nodules on exposed body parts; extracutaneous infections (termed phaeohyphomycosis) in subcutaneous tissues, sinuses, the brain, and other tissues may occur. Diagnosis is by appearance, histopathology, and culture. Treatment is with itraconazole, another azole, or flucytosine and surgical excision.
Chromoblastomycosis is a cutaneous infection affecting normal, immunocompetent people mostly in tropical or subtropical areas; it is characterized by formation of papillomatous nodules that tend to ulcerate. Pigmented fungi have been increasingly recognized as opportunists affecting immunosuppressed patients. These infections are caused by many kinds of dark, melanin-pigmented dematiaceous fungi including species of Bipolaris, Cladophialophora, Cladosporium, Drechslera, Exophiala, Fonsecaea, Phialophora, Xylohypha, Ochronosis, Rhinocladiella, Scolecobasidium, and Wangiella.
Symptoms and Signs
Most infections begin on the foot or leg, but other exposed body parts may be infected, especially where the skin is broken. Early small, itchy, enlarging papules may resemble dermatophytosis (ringworm). These papules extend to form dull red or violaceous, sharply demarcated patches with indurated bases. Several weeks or months later, new lesions, projecting 1 to 2 mm above the skin, may appear along paths of lymphatic drainage. Hard, dull red or grayish cauliflower-shaped nodular projections may develop in the center of patches and gradually extend to cover extremities for up to 4 to 15 yr. Lymphatics may be obstructed, itching may persist, and secondary bacterial superinfections may develop, causing ulcerations and occasionally septicemia.
Extracutaneous infections (phaeohyphomycosis) may occur. They include invasive sinusitis, sometimes with bone necrosis, as well as subcutaneous nodules or abscesses, keratitis, lung masses, osteomyelitis, mycotic arthritis, intramuscular abscess, endocarditis, brain abscess, and chronic meningitis.
Dematiaceous fungi only rarely cause fatal infections in patients who have normal, intact host defense mechanisms. Life-threatening illnesses occur more often in immunocompromised patients.
Late chromoblastomycosis lesions have a characteristic appearance, but early lesions may be mistaken for dermatophytoses. Phaeohyphomycosis must be distinguished from myriad other infectious and noninfectious conditions by histopathology and culture.
Dematiaceous fungi are frequently discernible in tissue specimens stained with conventional hematoxylin and eosin; they appear as septate, brownish bodies, reflecting their natural melanin content. Fontana-Masson staining for melanin confirms their presence. Culture is needed to identify the causative species.
Itraconazole is the most effective drug, although not all patients respond. Flucytosine is sometimes added to prevent relapse. Fluconazole seldom causes lesions to regress, and amphotericin B is ineffective. The role of voriconazole and posaconazole has not yet been determined.
Many cases require surgical excision for cure.
Last full review/revision April 2009 by Alan M. Sugar, MD
Content last modified February 2012