CYP2C19*17 genetic polymorphism--an uncommon cause of voriconazole treatment failure.

We describe an immunosuppressed, 48-year-old male, allogeneic hematopoietic stem cell transplant recipient with severe graft-versus-host disease who developed invasive pulmonary Aspergillus fumigatus infection 6 months after transplant. His lack of response to voriconazole and undetectable serum trough levels of the drug led us to establish that he had the uncommon cytochrome P450, CYP2C19*17 allele, which leads to a rapid metabolism of voriconazole but not of the other azole antifungals. We discuss the particular challenges encountered in this case.