<i>Rhinocladiella aquaspersa</i>, proven agent of verrucous skin infection and a novel type of chromoblastomycosis

We report a case of chromoblastomycosis which resembled sporotrichosis due to the presence of warty nodules and lymphatic distribution on the forearm in a 56-year-old male. Mycological and histopathological investigation of exudates and biopsy tissue samples revealed a granulomatous lesion with muriform cells, the hallmark of chromoblastomycosis. The infection showed only localized expansion with verrucous plaques suggesting a new clinical type of the disease. The causative agent was identified as Rhinocladiella aquaspersa. This case prompted a study of the clinical spectrum of R. aquaspersa, through which we identified a second case caused by this fungus in a 62-year-old Brazilian female. The case was unusual in that R. aquaspersa exhibited hyphae rather than muriform cells in tissue. Given the difficulties treating chromoblastomycosis and other infections caused by melanized fungi, we evaluated the in vitro activities of extended-spectrum triazoles, amphotericin B, and echinocandins against these clinical isolates of R. aquaspersa. Itraconazole (MIC; 0.063 mg/l) and posaconazole (MIC; 0.125 mg/l) had the highest in vitro activities, while voriconazole and isavuconazole had somewhat lower activities (MICs; 2 mg/l) against the isolates. Amphotericin B and anidulafungin each had an MIC of 1 mg/l, whereas the MIC of caspofungin was 8 mg/l.