Objective: To study prevalence, clinical, and laboratory characteristics from patients with fingernail onychomycosis caused by molds and compared findings with toenail onychomycosis.

Material and Method: The present study was retrospectively conducted in outpatient dermatology clinic of a university hospital between January 2012 and December 2014.

Results: One thousand four hundred ninety six nails from 1,102 patients presented with onychomycosis were included in the study. Among these nails, 221 (14.8%) were fingernails. Of patients with fingernail onychomycosis, 61.5% were male and the mean age (SD) was 53.1 (21.4) years. Thumbs were the most common site of onychomycosis infection (31.7%). Dermatophytes (DMPs) were the leading causative organism in fingernail onychomycosis (76.9%), including Trichophyton rubrum (53.4%), Trichophyton mentagrophytes (22.6%), and Trichophyton tonsurans (0.9%). Of patients who had non-dermatophyte molds (NDMs) fingernail onychomycosis (21.3%), the causative organisms were Fusarium spp. (14.5%), Aspergillus spp. (3.6%), and Neoscytalidium dimidiatum (2.7%). Four patients (1.8%) had mixed DMPs and NDMs infection. Comparing the fingernail and toenail groups, patients with fingernail onychomycosis were significantly younger (mean age 53.1 vs. 61.5, respectively, p-value <0.001). DMPs were more commonly found to be the cause of onychomycosis in fingernails than in toenails (76.9% vs. 68.4%, respectively, p-value <0.001).

Conclusion: Prevalence of fingernail onychomycosis was 14.8%. Thumbs were the most common site of fingernail onychomycosis. T. rubrum was the leading responsible organism. Patients with fingernail involvement were significantly younger, with DMPs being the most common causative organism than those with toenail involvement.

Keywords: Fingernail onychomycosis, Toenail onychomycosis, Molds, Dermatophytes, Non-dermatophytes