36-14: Mycetoma (Eumycetoma & Actinomycetoma)

Mycetoma is a chronic local, slowly progressive destructive infection that usually involves the foot; it begins in subcutaneous tissues, frequently after implantation of vegetative material into tissues during occupational activities. The infection then spreads to contiguous structures with sinus tracts and extruding grains. Eumycetoma (also known as maduromycosis) is the term used to describe mycetoma caused by true fungi. Actinomycotic mycetoma is caused by Actinomadura, Streptomyces, and Nocardia species. The disease begins as a papule, nodule, or abscess that over months to years progresses slowly to form multiple abscesses and sinus tracts ramifying deep into the tissue. Secondary bacterial infection may result in large open ulcers. Radiographs may show destructive changes in the underlying bone. Causative species can often be suggested by the color of the characteristic grains and hyphal size within the infected tissues, but definitive diagnosis requires culture.

The prognosis is good for patients with actinomycetoma, since they usually respond well to sulfonamides plus aminoglycosides. TMP-SMZ, 8/40/mg/kg/day orally for a 5-week cycle plus amikacin 15 mg/kg/day intravenously or intramuscularly in two divided doses for the first 3 weeks of the cycle has been reported to have excellent activity. Debridement assists healing but medical therapy is needed.

The prognosis for eumycetoma is poor, though surgical debridement along with prolonged oral itraconazole therapy, 200 mg twice daily, or combination therapy including itraconazole and terbinafine, may result in a response rate of 70% (Table 36–1). The various etiologic agents may respond differently to antifungal agents, so culture results are invaluable. Amputation is necessary in far advanced cases.