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Fusarium, a hyphomyocetous fungus, is often isolated from the environment as a laboratory contaminant, but is also known as a pathogen causing keratomycosis, onychomycosis, and opportunistic infection of the skin and viscera. We report a 67-year-old man with localized cutaneous fusariosis of the scrotum, as a complication of acute myeloid leukemia (AML) under chemotherapy. An induration of 25 mm in diameter, which was covered by necrosis and black crust and with pain upon pressure, was found on the scrotum. Direct microscopic examination of the necrosis showed numerous fungal elements. Culture on Sabouraud dextrose agar with cycloheximide yielded a floccose, grayish white colony. Microscopically, crescent-shaped macroconidia and oval microconidia were abundant. The fungus was identified using gene analysis as Fusarium falciforme of the Fusarium solani species complex. The lesion was treated by voriconazole (total dose: 66,180 mg) and was reduced to 15 mm in diameter. Other metastatic lesions did not appear. After 4 months from the first visit to our department, the patient died of AML. It is believed that the treatment in the early stage of infection prevented further extension of the lesion. During examination of necrotic lesions occurring on the skin of patients with hematological malignancies, it is important to include mycological examination for opportunistic fungal infections, such as aspergillosis or fusariosis, which are easily overlooked by routine culture methods using conventional media with cycloheximide. This paper summarizes cases of cutaneous fusariosis in Japan.

Molecular approaches are being developed to provide for the rapid and objective identification of fungi. We attempted the identification of Fusarium species by a genetic analysis to validate practically the utility of a molecular approach for fungal identification and to reveal its limitations, and sequenced three regions, the 5' end of the 28S rRNA gene (D2 region) and the internal transcribed spacer 1 and 2 (ITS1 and ITS2) regions, in the rRNA genes. The DNA sequences of 38 Fusarium strains isolated from domestic unpolished rice were compared for similarity with entries in the GenBank. Based on this comparison, it was estimated that all these three regions, as a minimum, must be compared with the database to identify Fusaria at the species level. According to the combinations of sequences in the three regions, the 38 isolates were classified into 13 groups. Out of the 13 groups, 6 groups (20 isolates in total) could be identified as definite species based only on the sequence data. For the other 6 groups (17 isolates in total), candidate species were limited on the basis of the sequence similarity, and then the isolates were identified at the species level with the aid of morphology. Only one isolate could not be identified. These results verified that DNA sequence comparison with the GenBank database is useful for the identification of Fusarium species.