Onychomycosis is the most common infectious nail disorder. Direct mycologic examination is still the cornerstone of diagnosis; however, it may take several weeks to obtain a result. Recently some dermoscopic patterns that can be useful in the diagnosis of onychomycosis were described. However, published data on dermoscopic features of onychomycosis are still limited.
We performed a prospective dermoscopic study of patients with positive fungal culture between April and December 2016. Patients with a final diagnosis of psoriasis or lichen planus were excluded from the study. Dermoscopy (polarized and nonpolarized) was performed.
Thirty-seven patients were enrolled, 24 women and 13 men (median ± SD age, 48.6 ± 16.1 years). Nail samples were culture positive for Trichophyton rubrum (89.2%), Trichophyton interdigitale (8.1%), and Candida albicans (2.7%). Distal and lateral subungual onychomycosis was the most frequent clinical subtype (59.5%). The most frequent dermoscopic features were subungual keratosis (73.0%), distal subungual longitudinal striae (70.3%), spikes of the proximal margin of an onycholytic area (59.5%), transverse superficial leukonychia (29.7%), and linear hemorrhage (13.5%). Brown chromonychia was most frequently seen with nonpolarized dermoscopy (66.6% versus 24%; P = .027).
Specific dermoscopic signs of onychomycosis are mostly related to the proximal invasion of the nail plate. Detection of these signs is simple and can, in some cases, help avoid mycologic testing.