Abstract:

Objective To report a case of superficial white onychomycosis caused by Nigrospora sphaerica. Methods Nail specimens were obtained from the patient and examined by direct microscopy, fungal culture and histopathology. Subsequently, the isolate was subjected to DNA sequencing analysis, gelatin liquefaction test, antifungal susceptibility test and nail-plate invasion test. Results A 21-year-old male presented with a 5-month history of whitening of the right hallux. Direct microscopy of nail scrapings showed spores, hyphae and lobiform conidiophores, and histopathology of decalcifying nail clippings revealed the presence of fungal elements including numerous spores and hyphae. A black woolly colony was formed in Sabouraud′s dextrose agar （SDA）. DNA sequencing analysis showed that the isolate was highly consistent with genus Nigrospora. Also, the isolate possessed the ability to liquefy gelatin and to invade normal nail plate. Antifungal susceptibility test showed that the isolate was highly susceptible to itraconazole, clotrimazole, amphotericin B and nystatin. The onychomycosis was cured after 5-month treatment with oral itraconazole pulse therapy. Conclusions The isolate is identified as Nigrospora sphaerica by morphological features and DNA sequencing analysis. It is the first reported case of superficial white onychomycosis caused by N. sphaerica in China, and it was effectively treated by itraconazole.