TC remains a significant public health problem across the globe; however, studies relating specifically to TC in adults are rare. Over recent years, the incidence of ATC has been increasing on a global level [8]. Here, we retrospectively analyzed the epidemiological characteristics and dermatophyte distribution of ATC in Hangzhou, eastern China.
Our analysis showed that the proportion of ATC (of all TC cases) was 19.7% in Hangzhou; this was significantly higher than the average value for proportion (9.04%) [7]. The rate of positive cultures for ATC was 54.5% (90/165); this exceeded the 28.04% (23/82) culture-positive rate reported for Korea in 2019 [9]. We also found that ATC predominantly infected females, especially those older than 45 years (35.2%). This was consistent with previous reports that ATC was more commonly detected in post-menopausal women [5, 7, 10]. This may be associated with reduced blood estrogen levels and the effects of this reduction on the sebaceous glands [6]. However, there have been some reports stating that ATC predominantly affects young women in Dakar, Senegal [11] and is slightly more prevalent in males in Hubei, China [8]. Therefore, the infection characteristics of ATC appear to differ by region; this requires further research.
The pathogenic fungi responsible for ATC can vary according to geographic area and time [8]. The anthropophilic dermatophyte T. violaceum is known as the most prevalent dermatophyte responsible for ATC globally; as reported in Egypt from 2002 to 2012 [12], Tehran (Iran) from 2010 to 2015 [5], southern Spain from 1995 to 2011 [13], Egypt from 1995 to 2011 [12], and Tunisia from 1990 to 2005 [14]. The anthropophilic dermatophyte T. rubrum was the most common dermatophyte in Italy between 2004 and 2012 [10]. M. audouiniiin and T. rubrum were the most common dermatophytes in Portugal between 2008 and 2018 [15]. Other reports showed that the most common dermatophyte was M. canis (42.48%) in southeastern Korea between 1989 and 2018 [3] and T. soudanense (65%) in Dakar (Senegal) [11]. However, in China, T. violaceum, M. canis, and T mentagrophyte were the most common etiological agents for ATC between 2000 and 2019 [7]. Wang et al. [16] reported that M. canis (49.0%) was the most common pathogen responsible for ATC in northern Taiwan between 2014 and 2019; T. violaceum (31.7%) was the second most common pathogen. He et al. [4] reported that T. violaceum has become the leading pathogen for recent ATC cases in Hubei, China. However, our current research showed that the most predominant dermatophytes were the anthropophilic dermatophytes T. violaceum and T. rubrum, followed by M. canis. We found that the proportions of T. violaceum and T. rubrum in adults (25.6% and 25.6%) were higher than in children (16.8% and 3.4%) [17]. Therefore, ATC infection is mainly caused by anthropomorphic dermatophytes; this differs from TC in children. In addition, ATC not only infects people with low-immunity; it also affects those with normal levels of immunity; these patients should be considered carefully in the clinic.
We retrospectively analyzed the potential causative agents of ATC. Our research revealed that 38.2% of patients had other aspects of tinea, which may have been transmitted by autoinoculation. In addition, 12.1% of patients had underlying diseases, consistent with previous reports stating that immunocompromised patients may be at higher risk of ATC infection [18]. Finally, only 2.4% of the patients analyzed had a history of pet exposure. Therefore, dermatologists are advised to consider that other aspects of tinea may be a risk factor in ATC.