Epidemiology of Onychomycosis in Chinese Mainland: A 30-year Retrospective Study

Background Onychomycosis was a common nail disease caused by dermatophytes, yeasts or molds. The prevalence of onychomycosis varied in different counties and it was necessary to understand the epidemiology in China. Objectives This study was conducted to investigate the epidemiology of onychomycosis in Chinese mainland in the past 30 years. Methods A 30-year systemic review was carried out by searching publications investigating the prevalence of onychomycosis in Chinese mainland from 1991 to 2020. Results A total of 90 articles involving more than 40,000 onychomycosis patients were enrolled in this study. The ratio of males to females was 1:1.32. Fingernail onychomycosis was found in 36.12% cases, toenail onychomycosis in 48.31%, and both fingernail and toenail onychomycosis in 15.57%. The most common clinical type of onychomycosis was distal lateral subungual onychomycosis (60.99%), followed by total dystrophic onychomycosis (18.91%), proximal subungual onychomycosis (10.19%) and superficial white onychomycosis (9.92%). Dermatophytes (60.59%) were the most frequently isolated pathogens, followed by yeasts (30.09%), molds (7.91%) and mixed infection (1.41%). The primary pathogens in dermatophytes, yeasts and molds were Trichophyton rubrum (49.93%), Candida albicans (10.99%) and Aspergillus (3.11%), respectively. Additionally, dermatophytes were more commonly affected males than females (63.69% vs. 51.57%), and mostly involved in toenail onychomycosis (75.63%). The infection of yeasts was higher in females than males (40.97% vs. 29.52%), often causing onychomycosis in fingernail than toenail (41.03% vs. 17.08%), and it was more common in warm and humid southern regions than northern area (34.07% vs. 24.41%). Conclusion The proportion of the causative agents changed over time, dermatophytes, especially T. rubrum had always been the predominant pathogen, followed by yeasts and molds. The distribution of fungal pathogens varied among clinical types, gender, infection sites and geography gender.