Trichophyton mentagrophytes genotype VII

Overview

• Trichophyton mentagrophytes type VII (TMVII) is a recently emerged dermatophyte that is closely related to T. indotineae (note: T. indotineae was previously called T. mentagrophytes type VIII).^1-3

• TMVII spreads between people and may be transmitted via sexual contact, including in specific patient populations such as men who have sex with men or persons who travelled to Southeast Asia for sex tourism.^1-4

• Unlike T. indotineae (Which may also spread via sexual contact), resistance to terbinafine has not been reported to date among TMVII.

• Current reports indicate that some patients have been prescribed topical steroids before receiving a correct tinea diagnosis, which masked the typical features of tinea. This may result in delays in care and ongoing transmission.

Epidemiology

• Data indicate that TMVII infections have been circulating locally in Europe for at least several years.^1,5

• In 2024, a TMVII case was reported in the United States.⁴ It is unknown whether this infection was acquired in Europe or in the United States.

• A 2024 NYC MMWR identified multiple TMVII cases, including in patients without travel, suggesting possible early domestic transmission.⁶

• Additional case reports from Spain, Japan, and other countries further expand the known geographic range.^7-9

• Incubation period: Limited data suggest symptoms may develop within several days to a few weeks after exposure, although precise timing remains undefined, and longer incubation periods have been suggested.^1,5

• Asymptomatic carriage is considered possible but has not been conclusively demonstrated. Presymptomatic transmission is also suspected, though definitive evidence is lacking.^5,10

Clinical features

• Lesions typically involve the genital, perineal, and perianal areas but may also occur on the face or other shaved/waxed sites with skin barrier compromise. Typical lesions of tinea corporis may also be seen.

• Lesions may mimic eczema or psoriasis.

• Deep follicular or nodular involvement can occur and may contribute to prolonged treatment needs.

• Lesions may be markedly inflammatory (nodules, kerion-like plaques, Majocchi-type involvement) and may mimic mpox, HSV, or bacterial infections.¹

• Coexisting STIs have been reported in some patients.¹

• Bacterial superinfection and scarring have rarely been reported.¹

Clinical appearance of Trichophyton mentagrophytes genotype VII infections in men in France, 2022.⁵

A) Swollen lesions above the upper lip and B) on the beard (kerion). C) Papular and nodular inguinal lesions. D) Peri-anal mpox lesions with associated papules and pustules with central umbilication and a large lesion with a central necrotic crust, surrounded by extensive erythemato-squamous circinate lesions caused by TMVII infection. (Source: https://wwwnc.cdc.gov/eid/article/29/7/23-0025-f1)

Diagnosis

• Routine culture may identify either Trichophyton mentagrophytes or Trichophyton interdigitale. Identification of TMVII requires specialized testing (e.g., ITS genome sequencing) available only at select laboratories (see “Diagnosing Antimicrobial-resistant dermatophytosis”

• KOH preparation is a quick tool to support a diagnosis of dermatophyte infection while awaiting culture or sequencing.

• No point-of-care molecular assays specific for TMVII are currently available.

Treatment

• Most published regimens use oral terbinafine 250 mg daily; case series indicate many patients require 6–12 weeks of therapy, with some requiring longer for deep or highly inflammatory lesions.^1,6,7,9

• In cases with inadequate response after several weeks of terbinafine, itraconazole has been successfully used as second-line therapy despite no confirmed terbinafine resistance in TMVII to date.

• Topical antifungal agents may be helpful as adjunctive therapy but are not recommended as monotherapy for TMVII given limited evidence of efficacy.⁶

• Clinicians are encouraged to monitor patients throughout treatment for disease resolution.

• Some experts recommend extending therapy 2–4 weeks beyond clinical resolution to reduce relapse risk, although evidence is limited.

Counseling and prevention

Physicians can council patients on several points:

• Transmission to others is possible when lesions are present. Skin-on-skin contact is currently considered the most likely source of transmission.

• Patients should be screened for other sexually transmitted infections, and partner notification and screening should be discussed.

• Partners should be evaluated if symptomatic; routine screening of asymptomatic partners is not currently recommended.

• The need for prolonged therapy.

• The importance of adherence to the medication and follow-up.

• The need to avoid sharing personal items and clothing. The risk of transmission from fomites and how long the spores live in the environment is unknown.

• Clothing, towels, bedding, and similar shared items should be laundered on high heat. The risk for transmission from fomites and how long the spores live in the environment is unknown.

• The possibility of relapse or recurrence.

• Potential side effects from antifungals.

• Dermatophyte spores can be killed with common disinfectants like diluted chlorine bleach (1/4 cup per gallon of water), benzalkonium chloride, or strong detergents, such as common all-purpose or heavy-duty household cleaners.

• If pets are present in the home and also develop skin lesions, the pet should be evaluated by a veterinarian.

Knowledge gaps

• Incubation period (partially described but not well defined).

• Optimal systemic treatment duration.

• Role and effectiveness of topical monotherapy.

• Predictors of treatment failure.

• Whether asymptomatic carriage and presymptomatic infection can occur.

Additional resources