Invasive zygomycosis in hematopoietic stem cell transplant recipients receiving voriconazole prophylaxis.

We report 4 cases of invasive zygomycosis in hematopoietic stem cell transplant recipients, all occurring after May 2003, when voriconazole began to be used as antifungal prophylaxis. No cases of zygomycosis had been detected in this population in the 3 years prior to May 2003. All 4 patients were receiving immunosuppressive therapy for presumed graft-versus-host disease. Profoundly immunosuppressed patients receiving voriconazole prophylaxis remain at risk for less-common pathogens that are intrinsically resistant to this agent.