Kerion Celsi due to Microsporum canis in an Adult Woman, Treated Successfully with Fosravuconazole

A 64-year-old woman presented with a fist-sized, severely painful lesion with scales, crusts, pustules, erythema with subcutaneous abscess, and hair loss on the left temporal region. Direct microscopic examination revealed a large number of spores around the hair, which indicated ectothrix hair invasion, and some hyphae were also found. Histopathological examination showed significant inflammatory cell infiltration from the dermis to the subcutaneous tissues and into the hair follicles, destruction of the hair follicles with granulomatous reactions, and fungal masses along the hair within the hair follicles. Microsporum canis was identified based on morphological features via culture method and molecular biological analysis of the internal transcribed spacer region DNA sequence. The patient was diagnosed with kerion celsi caused by M. canis. For treatment of kerion celsi, we chose an oral antifungal agent, fosravuconazole (FRVCZ), which has been available since 2018 only in Japan. Clinical symptoms were cured in 12 weeks without scarring. No side effects were observed during oral administration of FRVCZ. The results of our case and several previous reports suggest that FRVCZ is effective in treating various types of dermatomycoses.