Increasing Prevalence of Trichophyton rubrum Identified through an Analysis of 115,846 Cases over the Last 37 Years

Trichophyton rubrum is the most common dermatophyte in the world with the highest prevalence in Korea. There are few reports about epidemiological and mycological characteristics of T. rubrum based on long-term, large-scale studies. The purpose of this study was to investigate the clinical and epidemiological characteristics of T. rubrum infections in Korea. We retrospectively investigated with patients' records about the epidemiological and mycological status of 115,846 cases with T. rubrum infection that was mycologically diagnosed at Catholic Skin Disease Clinic from 1979 to 2013. Direct microscopy in 15% KOH solution and culture was done in each case. The annual incidence of patients with T. rubrum infection had been increasing during the period; and of 131,122 patients with dermatophytosis, 115,846 patients (88.35%) had T. rubrum infection. Disease was most prevalent among patients in their twenties in the 1970s and 1980s; in their thirties in the 1990s; in their forties in the 2000s; and in their fifties in the 2010s. The sex ratio was 1.5:1. T. rubrum infection was most commonly seen in summer and was found predominantly in patients living in urban areas. Toe webs were most frequently involved, followed by toenails and groin. This epidemiologic findings provide useful information for prevention of T. rubrum infection and future dermatophytosis prospects. Graphical Abstract Keywords: Dermatophytosis, Epidemiology, Incidence, Mycology, Trichophyton rubrum INTRODUCTION Fungal infections are influenced by interactions between the host, the infectious agents, and the environment (1). During the past 80 yr, there have been dramatic changes in Korean dermatophytosis, including common causative agents of dermatophytosis and clinical characteristics (2,3,4,5,6,7,8). These have resulted from changes in socioeconomic status, lifestyle, and population, as well as the development of new antifungal drugs and diagnostic methods. Therefore, an epidemiologic study will provide useful information for prevention of infection and future dermatophytosis prospects. Trichophyton rubrum, T. mentagrophytes, Microsporum canis, Epidermophyton floccosum, T. verrucosum, M. gypseum, M. ferrugineum, T. tonsurans, T. schoenleinii, and T. violaceum have been isolated in Korea (9,10,11,12,13,14,15,16,17,18). T. rubrum has been known to be a main causative agent in dermatophytosis in Korea since the 1960s (2). T. tonsurans was newly introduced to Korea in the 1980s (10). Conversely, T. schenleinii has disappeared from Korea (8). Similarly, T. mentagrophytes and M. canis have been decreasing in prevalence since the 2000s (19, 20). We conducted this study to investigate the clinical and epidemiological characteristics of T. rubrum infection in Korea through the retrospective analysis of medical records of 115,846 patients infected with T. rubrum from 1979 to 2013.