Mucor ramosissimus Samutsevitsch isolated from a thigh lesion.

Mucor ramosissimus Samutsevitsch is presented for the first time as an etiologic agent of cutaneous zygomycosis in a patient with aplastic anemia on immunosuppressive therapy. This report also represents the third case caused by this species reported in the literature. A biopsy taken from a lesion on the patient's thigh revealed broad, nonseptate, nonbranching hyphae compatible in morphology with a Zygomycete; M. ramosissimus was cultured twice from the thigh lesion. The patient was treated successfully with amphotericin B. Identifying features of M. ramosissimus include the following: numerous sporangia lacking columellae and resembling those of Mortierella spp., short, erect sporangiophores repeatedly branching sympodially; tough, persistent, and diffluent sporangial walls; numerous oidia in chains; extremely low colonies; and restricted growth at 36 degrees C. This paper describes the isolate and strives to alert the clinical microbiologist to this rarely reported pathogen.