Abstract: Objective To report a case of chromomycosis caused by Phialophora verrucosa and explore the laboratory features of the pathogen. Methods Skin lesion was examined by histopathology and fungus culture. The morphology of the isolate was observed by microscopy and scanning electron microscopy. The coenzyme Q system of this isolate was analyzed by HPLC assay. The DNA sequences of LSU rDNA D1/D2 region of this isolate and a standard fungus strain were compared. Results The initial lesion was an erythematous papule that subsequently developed into one or multiple coalescing warty papules or plaques slowly. The bronze-colored spores could were observed in the dermis or macrophages. The isolate grew very slowly, requiring 4 weeks of incubation. Microscopically, no characteristic structures were found on Sabourand's dextrose agar, while there were vase-like structures, which were referred to as phialides on potato dextrose agar (PDA) and corn meal agar I (CMA-I). The phialides on PDA mostly grew at the top of hypha, but on CMA-I they mostly grew on the side of hypha. The isolate contained coenzyme Q-10, and its DNA sequence of LSU rDNA D1/D2 region completely consistent with those of the standard strain. Conclusion Chromomycosis caused by Phialophora verrucosa is rare in China. It can be diagnosed by fungus culture and histopathological examination. Coenzyme Q system analysis and DNA sequencing can exclude the interference from different phenotypes.

Key words: Phialophora, Chromoblastomycosis, Ubiquinone, Sequence analysis, DNA