Shifting etiological agents of dermatophytosis: a molecular epidemiological study from Iran

Dermatophytosis is a significant worldwide health concern, particularly in tropical and subtropical regions. Tinea unguium (TU) and Tinea capitis (TC) are among the most prevalent clinical manifestations of dermatophytosis caused by several dermatophyte fungi. This study investigated the molecular epidemiology and distribution of dermatophytes causing TU and TC in Tehran, Iran.

From March 2023 to March 2024, a clinical mycology center in Tehran received 342 suspected cases of TU and TC. The diagnostic methods included the conventional and molecular methods by sequencing the ITS region of ribosomal DNA.

Overall prevalence of dermatophytosis was 59/342 (17.2%) among suspected patients by direct examination. TU and TC were diagnosed in 31/59 (53%) and 28/59 (47%), respectively. The final prevalence among suspected patients was 43/342 (12.5%) by PCR-sequencing, and TC accounted for the largest group of them, 25/43 (58%). Females represented the largest group of suspected TU cases (204/303, 67%; mean age: 57 years), while males predominated among TC patients (28/39, 74%; mean age: 10 years). PCR-sequencing revealed Trichophyton tonsurans was the most common agent of TC, 22/25 (88%), and Trichophyton indotineae emerged as a notable cause of TU in 5/18 (28%) of confirmed cases.

In our study, T. tonsurans remained the predominant cause of TC, while T. indotineae emerged as a significant cause of TU. Agreement between conventional and molecular methods was substantial (κ=0.73, 95% CI: 0.61-0.85), with 81.8% misidentification of the T. mentagrophytes complex but complete accuracy for T. tonsurans and Microsporum canis.