Abstract: Objective To isolate and observe Pityrosporum yeasts from a patient with onychomycosis. Methods The involved nail specimens were investigated by means of culture, pathological and scanning electron microscopic examination and 20% KOH preparation. Results Physical examination showed that each finger and toe nail appeared brownish black, rough and thick, some of the fore part of the nail plate detached from the nail bed. Fingernail specimen's culture results showed that Trichophyton rubrum grew on Sabouraud's dextrose agar and Pityrosporum ovale grew on the medium containing rapeseed oil. The pathological examination revealed P.ovale yeast involvement in the fissure of the nail plate. Under the scanning electron microscopy, a lot of P.ovale yeasts with characteristic collarette structure inserted in the nail tissue was noticed. In the 20% KOH preparations of nail incubated at 56℃ for 1h and stained with Quink Parker ink, spores and hyphae were identified morphologically with P.ovale and T.rubrum respectively. The patient received intermittent pulse therapy with itraconazole, the color of the nails became much brighter 1 to 2 months after the fourth cycle of therapy, but no further improvement was observed afterwards. P.ovale and T.rubrum grew again 6 months after treatment when the clippings of the fingernail were cultured. Conclusion This is the first document of onychomycosis related with P.ovale in China.

Key words: Onychomycosis, Pityrosporum ovale, Trichophyton rubrum, Microscope, electron