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Onychomycosis: Epidemiology, clinical features, and diagnosis

Adam O Goldstein, MD, MPH
Section Editors
Robert P Dellavalle, MD, PhD, MSPH
Moise L Levy, MD
Ted Rosen, MD
Deputy Editor
Abena O Ofori, MD


Onychomycosis refers to nail infections caused by fungi, including dermatophytes (tinea unguium), yeasts, and nondermatophyte molds. The major clinical presentations of onychomycosis are distal lateral subungual onychomycosis (picture 1A-B), white superficial onychomycosis (picture 2), and proximal subungual onychomycosis (picture 3A-C). Additional clinical manifestations are endonyx onychomycosis (infection limited to the nail plate and sparing the nail bed), total dystrophic onychomycosis (picture 4), and mixed pattern onychomycosis.

The epidemiology, clinical features, and diagnosis of onychomycosis will be reviewed here. The management of onychomycosis and the differential diagnosis of nail dystrophy are reviewed separately. (See "Onychomycosis: Management" and "Overview of nail disorders".)


Onychomycosis is a common disorder that is estimated to account for 50 to 60 percent of abnormal nails [1]. Population-based studies have found varied estimates of prevalence, ranging from less than 1 percent to 8 percent in Europe and the United States and less than 1 percent in central Africa [2]. A systematic review of population-based studies that assessed the prevalence of culture-proven dermatophyte, yeast, and nondermatophyte mold onychomycosis of the toenails found pooled prevalences of 3.22 percent (95% CI 3.07-3.38), 0.40 percent (95% CI 0.34-0.47), and 0.37 percent, (95% CI 0.32-0.43), respectively [3].

Onychomycosis is much more common in adults than in children. The systematic review found pooled prevalences of pediatric dermatophyte and yeast toenail onychomycosis of 0.14 percent (95% CI 0.11-0.18) and 0.09 percent (95% CI 0.06-0.13), respectively [3].

Onychomycosis occurs in both sexes. Most, but not all studies have found higher prevalences in males than in females [2].


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Literature review current through: Sep 2016. | This topic last updated: Apr 26, 2016.
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