Other fungi causing onychomycosis.

Nondermatophyte onychomycosis account for 2% to 12% of all nail fungal infections and can be caused by a wide range of fungi, mainly Scopulariopsis brevicaulis, Aspergillus versicolor, A. flavus, A. niger, A. fumigatus, Fusarium solani, F. oxysporum and Scytalidium spp. Among the predisposing factors are footwear, hyperhidrosis, local trauma, peripheral circulatory disease, and immunosuppression. These nondermatophyte fungi lack the keratinolytic capacity of dermatophytes, but they still can infect alone or in combination with the latter. Because most are considered laboratory contaminants, special criteria have been created for the correct diagnosis of nondermatophyte onychomycosis. The etiologic agent does not determine the clinical pattern of nail invasion, but superficial onychomycosis is frequently observed; leukonychia and melanonychia can also be clinical manifestations.