Primary invasive cutaneous Microsporum canis infections in immunocompromised patients.

Two cases of primary invasive cutaneous infections caused by the zoophilic dermatophytic species Microsporum canis are presented. The first case occurred in a liver transplant recipient who was receiving immunosuppressive therapy. Multiple erythematous papules were seen on both legs, and a biopsy revealed invasive fungal hyphae. The second case was diagnosed in a human immunodeficiency virus-positive individual with a CD4 lymphocyte count of 81 mm3. Raised red nodules were seen on her scalp and face. Histopathology was consistent with bacillary angiomatosis, and in addition, invasive septate hyphae were observed. The two strains recovered from the biopsy specimens from both individuals had colony morphologies consistent with that of M. canis, but it was difficult to induce production of macroconidia. These cases serve to increase the awareness of this unusual infection, reinforce the need for cultures, and raise some interesting questions about the potential virulence of this dermatophyte species.