Recalcitrant tinea infections due to Trichophyton indotineae in the United States (2025-2026): a retrospective case series identified by real-time PCR.

UNLABELLED: Trichophyton indotineae is an emerging dermatophytic pathogen causing severe infections that are frequently resistant to standard antifungals. Since 2015, this species has spread intercontinentally.

OBJECTIVES

To highlight the clinical characteristics and challenges in managing T. indotineae infections in the United States and to introduce the utility of rapid real-time PCR (qPCR) diagnosis.

METHODS

Records from a molecular diagnostics laboratory (Bako Diagnostics, GA, USA) were retrospectively reviewed for T. indotineae detections between May 2025 and January 2026. Cases were identified using a novel single-plex qPCR assay and confirmed by sequencing of the internal transcribed spacer region. The squalene epoxidase gene (SQLE) was sequenced to assess terbinafine resistance. A survey was distributed to treating physicians to collect information on recent international travel, household transmission, clinical features, immunosuppressive medications or conditions, and treatment history.

RESULTS AND

CONCLUSIONS

All patients (median age: 54; 3 males and 2 females) reported recent travel to India or Nepal, except one, who was the spouse of a patient who had traveled to India. Two different SQLE substitutions were detected, F397L (N = 2) and L393F (N = 1), which are common among terbinafine-resistant T. indotineae isolates found globally. Potential gaps in clinical management - attributed to treatment initiation prior to confirmatory diagnosis of T. indotineae - were identified. These gaps include the use of topical corticosteroids, lack of itraconazole use (100-200 mg/day for 6-8 weeks or longer) as first-line treatment, and prescribing fixed, short treatment durations. In T. indotineae cases, these practices may increase the risk of disease recurrence and domestic spread. Current clinical recommendations are summarized herein, highlighting the utility of this novel qPCR assay for real-time treatment decision-making.