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Trichophyton indotineae

Trichophyton indotineae, also known as Trichophyton mentagrophytes ITS genotype VIII, is a newly identified dermatophyte mold that has been associated with a near epidemic level of chronic, refractory, and severe dermatophyte infections in areas of South Asia. It is now reported globally.  Infections can be followed by widespread, highly pruritic, scaly, and erythematous plaques of tinea corporis, cruris, or face. Lesions may rapidly spread and show variable degrees of inflammation. Varied morphologies are reported, including tinea incognito and tinea pseudoimbricata. Infections can spread easily among close contacts, who may report inappropriate use of topical steroids. High-level resistance to terbinafine, an often used first-line antifungal agent, is characteristic, and decreased responsiveness to griseofulvin and azoles has also been noted. The current treatment of choice is oral itraconazole, typically for a 6-week to 8-week duration or longer; however, relapse even after 8 weeks of therapy with high doses of itraconazole has been reported. Patients may develop posttinea xerosis and persistence of itch.

As with the current patient, travel history should be gathered and suspicion raised when patients present with widespread, inflamed, or atypical appearing plaques of tinea, especially when they were refractory to first-line or second-line therapies. Morphologic overlap among dermatophytes leads to potential misidentification of T indotineae on culture results as T mentagrophytes or Trichophyton interdigitale.2 The diagnosis is confirmed by genetic sequencing of the ITS region in specialized laboratories.

References

Uhrlaß  S, Verma  SB, Gräser  Y,  et al.  Trichophyton indotineae–an emerging pathogen causing recalcitrant dermatophytoses in India and worldwide—a multidimensional perspective.   J Fungi (Basel). 2022;8(7):757. doi:10.3390/jof8070757

Caplan  AS, Chaturvedi  S, Zhu  Y,  et al.  Notes from the field: first reported U.S. cases of tinea caused by Trichophyton indotineae—New York City, December 2021-March 2023.   MMWR Morb Mortal Wkly Rep. 2023;72(19):536-537. doi:10.15585/mmwr.mm7219a4

Caplan AS et al.Trichophyton mentagrophytes Internal Transcribed Spacer Genotype VIII, published onlineJuly 7, 2023. doi:10.1001/jamadermatol.2023.2645

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