First Molecular Confirmation of Trichophyton indotineae in South Korea: A Case Report

Trichophyton indotineae is an emerging terbinafine-resistant dermatophyte within the T. mentagrophytes/T. interdigitale complex. Herein, we describe the first two confirmed Korean cases of T. indotineae infection. Both patients had chronic and extensive dermatophytosis involving the trunk, buttocks, thighs, and groin in case 1 and confined to the right lower leg and ankle in case 2. In both cases, the eruption failed to respond to terbinafine or itraconazole and was aggravated by intermittent corticosteroid use. Cultures produced white cottony colonies with grape-like microconidia and negative urease reactions. Internal transcribed spacer (ITS) region sequencing identified T. indotineae, and analysis of the squalene epoxidase (SQLE) gene showed L393F mutation, which was associated with terbinafine resistance. Antifungal susceptibility testing revealed terbinafine resistance but susceptibility to itraconazole. After withdrawal of corticosteroids and maintenance of continuous itraconazole therapy, case 1 showed near-complete clinical remission with minimal residual scaling, whereas case 2 achieved complete clinical and mycological remission. These findings suggest possible local transmission and emphasize the importance of molecular confirmation and antifungal stewardship in Korea.