The world crisis of terbinafine-resistant Trichophyton indotineae until 2024: do we have enough knowledge?

Dermatophytoses is a well-known name among dermatologists due to its high prevalence among various ages of humans. It is mainly caused by skin-infecting fungi called dermatophytes. From these dermatophytes, Trichophyton indotineae is a newly virulent species with high prevalence and multidrug properties. It was first described in the Indian subcontinent as a closely genetically related strain to Trichophyton interdigitale and Trichophyton mentagrophytes, and spread quickly worldwide. Terbinafine has been utilized for the treatment of dermatophytosis caused by T. indotineae owing to the development of resistance to azole in many of its strains. Wide use of terbinafine has also induced later the development of terbinafine-resistant strains of T. indotineae. Point mutations in the squalene epoxidase (SQLE) gene, which lead to single or multiple substitutions in amino acid positions in the encoded protein (SQLE), are the main reason for antifungal resistance in T. indotineae. This review aims to determine the background of terbinafine-resistant strains of T. indotineae and where they are currently located.