Onychomycosis: Correlation between the dermoscopic patterns and fungal culture

Onychomycosis is a dermatophyte fungal infection of the nail plate, bed, and the matrix, leading to the gradual damage which often considered a cosmetic problem. Several presentations of onychomycosis: distolateral subungual (DLSOM), superficial white, proximal subungual, endonyx, and total dystrophic (TDOM). Although the diagnosis relies on mycological results, there are three specific dermoscopic findings for onychomycosis: a jagged edge of the onycholytic area, with spikes directed to the proximal fold, white-yellow longitudinal striae in the onycholytic nail plate, and colored parallel bands.

The objective of this diagnostic cross-sectional study was to evaluate the diagnostic accuracy of dermoscopy as a low-cost tool compared with fungal culture in patients with onychomycosis.

This study was carried out on 40 patients with a clinical diagnosis of onychomycosis collected from dermatology outpatient clinic of Alzahraa University Hospital after approval from the research ethics committee of Al-Azhar University. For each patient, dermoscopic imaging of nail was done. And nail scrapings, culture on sabouraud's dextrose agar medium, and dermatophyte test agar medium. Informed written consent was taken from all patients, and the data collected from dermoscopic and laboratory results were statistically evaluated.

Concerning the dermoscopic features, longitudinal white striae, jagged proximal edge with spikes, were the most commonly detected in DLSOM and TDOM. Linear edge was exclusive to traumatic onycholysis. Laboratory results: Aspergillus species was the most common detected fungus (45%) followed by Candida (32.5%).

Dermoscopy could facilitate the diagnosis of onychomycosis and differentiate it from mycologically negative onycholysis.