Mucormycosis (Zygomycosis; Phycomycosis)

Infection with tissue invasion by broad, nonseptate, irregularly shaped hyphae of diverse fungal species, including Rhizopus, Rhizomucor, Absidia, and Basidiobolus.

Infection is most common in immunosuppressed persons, in patients with poorly controlled diabetes, and in patients receiving the iron-chelating drug desferrioxamine.

Symptoms and Signs

Rhinocerebral mucormycosis is the most common form, but primary cutaneous, pulmonary, or GI lesions sometimes develop, and hematogenous dissemination to other sites can occur. Rhinocerebral infections are usually fulminant and frequently fatal. Necrotic lesions usually appear on the nasal mucosa or sometimes the palate. Vascular invasion by hyphae leads to progressive tissue necrosis that may involve the nasal septum, palate, and bones surrounding the orbit or sinuses. Manifestations may include pain, fever, orbital cellulitis, proptosis, purulent nasal discharge, and mucosal necrosis. Progressive extension of necrosis to involve the brain can cause signs of cavernous sinus thrombosis, convulsions, aphasia, or hemiplegia. Patients with diabetic ketoacidosis are most often affected, but opportunistic infections may also develop in association with renal desferrioxamine therapy in chronic renal disease or with immunosuppression, particularly with neutropenia or high-dose corticosteroid therapy. Pulmonary infections resemble invasive aspergillosis. Cutaneous Rhizopus infections have developed under occlusive dressings.

Diagnosis and Treatment

Diagnosis requires a high index of suspicion and painstaking examination of tissue samples for large nonseptate hyphae with irregular diameters and branching patterns, because much of the necrotic debris contains no organisms. For unclear reasons, cultures usually are negative, even when hyphae are clearly visible in tissues. CT scans and x-rays often underestimate or miss significant bone destruction.

Effective antifungal therapy requires that diabetes be controlled or, if at all possible, immunosuppression reversed or desferrioxamine discontinued. IV amphotericin B must be used, because azoles are ineffective. Surgical debridement of necrotic tissue may be needed, because amphotericin B cannot penetrate into these avascular areas to clear remaining organisms.