Breakthrough Fusariosis in a Patient with Acute Lymphoblastic Leukemia Receiving Voriconazole Prophylaxis

SIR—Voriconazole is a broad-spectrum triazole antifungal drug with excellent activity against Aspergillus species, most Candida species, and several less-common invasive fungi but with limited activity against pathogenic Zygomycetes. Reports on the successful use of voriconazole therapy for patients with invasive fusariosis [1–3] and in vitro studies showing that the MICs of voriconazole against Fusarium species are usually lower than the MICs of itraconazole and are frequently lower than the MICs of amphotericin B [4, 5] seem to suggest a promising role for voriconazole as a life-saving therapy for immunocompromised hosts with Fusarium infections. For these reasons, the US Food and Drug Administration approved voriconazole for the treatment of Fusarium infection in patients intolerant of or with an infection refractory to other drugs. Given its broad spectrum and the availability of both oral and intravenous formulations, voriconazole has also been used as antifungal prophylaxis instead of fluconazole, a drug without antimold activity [6–8]. However, the occurrence of breakthrough fungal infections in patients receiving long-term voriconazole therapy has been reported recently. Most of these infections were due to Zygomycetes, but infections with other fungal species have also been observed in these patients [6–8]. Here, we describe a case of breakthrough fusariosis in a patient with acute lymphoblastic leukemia (ALL) receiving long-term voriconazole prophylaxis.