Global prevalence of onychomycosis in general and special populations: An updated perspective

BackgroundOnychomycosis is a chronic nail disorder commonly seen by healthcare providers; toenail involvement in particular presents a treatment challenge.ObjectiveTo provide an updated estimate on the prevalence of toenail onychomycosis.MethodsWe conducted a literature search using PubMed, Embase and Web of Science. Studies reporting mycology‐confirmed diagnoses were included and stratified into (a) populations‐based studies, and studies that included (b) clinically un‐suspected and (c) clinically suspected patients.ResultsA total of 108 studies were included. Based on studies that examined clinically un‐suspected patients (i.e., with or without clinical features suggestive of onychomycosis), the pooled prevalence rate of toenail onychomycosis caused by dermatophytes was 4% (95% CI: 3–5) among the general population; special populations with a heightened risk include knee osteoarthritis patients (RR: 14.6 [95% CI: 13.0–16.5]), chronic venous disease patients (RR: 5.6 [95% CI: 3.7–8.1]), renal transplant patients (RR: 4.7 [95% CI: 3.3–6.5]), geriatric patients (RR: 4.7 [95% CI: 4.4–4.9]), HIV‐positive patients (RR: 3.7 [95% CI: 2.9–4.7]), lupus erythematosus patients (RR: 3.1 [95% CI: 1.2–6.3]), diabetic patients (RR: 2.8 [95% CI: 2.4–3.3]) and hemodialysis patients (RR: 2.8 [95% CI: 1.9–4.0]). The prevalence of onychomycosis in clinically suspected patients was significantly higher likely due to sampling bias. A high degree of variability was found in a limited number of population‐based studies indicating that certain pockets of the population may be more predisposed to onychomycosis. The diagnosis of non‐dermatophyte mould onychomycosis requires repeat sampling to rule out contaminants or commensal organisms; a significant difference was found between studies that performed single sampling versus repeat sampling. The advent of PCR diagnosis results in improved detection rates for dermatophytes compared to culture.ConclusionOnychomycosis is an underrecognized healthcare burden. Further population‐based studies using standardized PCR methods are warranted.