Terbinafine-resistant Trichophyton indotineae in two Italian MSM: a new emerging sexually transmissible infection

We report, to the best of our knowledge, the first two cases of Trichophyton (T.) indotineae infection observed in a couple of Italian engaged men who have sex with men (MSM), potentially acquired through sexual contact with a third man from India. This article also provides a narrative review of the most recent existing literature on the potential sexual transmission of genital dermatophytoses. For dermatophytosis sexual transmission is a presumptive diagnosis but some clinical criteria may raise suspicion of sexual transmission, such as the occurrence of genital lesions in individuals with high-risk sexual behavior, without simultaneous involvement of the feet and/or nails, without a history of contact with infected animals, and the presence of similar lesions in sexual partners. In recent years, several reports have indicated a potential sexual transmission of genital dermatophytosis, mainly caused by T. mentagrophytes genotype VII (TMVII), first observed in heterosexual individuals and then also in groups of MSM, suggesting a potentially unnoticed epidemic at the European level. From 2020 onwards, the emergence of T. indotineae, a novel strain closely related to TMVII, yet often associated with Terbinafine resistance, has been documented in more than 30 countries worldwide. Laboratory identification requires advanced molecular techniques, as culture-based methods are unable to differentiate T. indotineae from other Trichophyton species. A proper species-level diagnosis is essential to establish the appropriate treatment. Dermatologists should be aware of the international spread of this new strain and its potential sexual transmission and conduct targeted mycological tests in at-risk populations.