A difficult-to-treat form of ringworm can be sexually transmitted and has now been found in the United States. Ringworm, also known as tinea, is a skin infection caused by a variety of fungi. In this case, the culprit is a fungus called Trichophyton mentagrophytes type VII (TMVII). It has previously been reported in Southeast Asia and Europe. In 2023, for example, doctors in Paris published a case series of 13 infections reported among men in the city. These recent cases occurred among men who have sex with men, suggesting that the fungus may now be circulating in this demographic, although anyone can become infected.
In a paper published June 5 in the journal JAMA Dermatology, doctors in New York City reported what they believe is the first case in the U.S. The man, who was in his 30s, developed scaly, red patches around his groin, genitals, and buttocks, as well as on his legs, arms, and back. He had just returned to New York after traveling to England, Greece, and California when the rash appeared. He told doctors he had had several male sexual partners while traveling, though none of them had a similar rash.
A skin biopsy from the man’s thigh confirmed that he had ringworm, and he was prescribed antifungal medication. The infection had still not cleared up after a month, so doctors took a sample of the fungus and found it to be TMVII. The man’s antifungal regimen was then adjusted, first to one drug, then to another, as his condition steadily improved.
TMVII infections can take months to resolve, even with medication, but the antifungal drug terbinafine appears to be particularly effective, the team reported. If TMVII is suspected or diagnosed, the infected person’s sexual partners should be tested, and the patient should be evaluated for additional sexually transmitted infections, they added.
Doctors have reported the first known case of the infection in the United States, following cases in Europe and Asia. KATERYNA KON/SCIENCE PHOTO LIBRARY
“Dermatologists in the United States should be aware of TMVII infections,” the doctors wrote in their report. “Timely treatment can reduce the risk of scarring and transmission.” TMVII looks like typical ringworm but can be more inflammatory and thus cause abscesses and scarring if left untreated.
Doctors may have to ask patients direct questions to identify more cases, the doctors said in a statement.
“Because patients are often reluctant to discuss genital problems, clinicians should ask directly about rashes in the groin and buttock areas, especially in those who are sexually active, have recently traveled abroad, and report itchy areas elsewhere on the body,” senior study author Dr. John Zampella, an assistant professor of dermatology at NYU Grossman School of Medicine, said in a statement.
Doctors noted in their report that using standard laboratory methods, it is difficult to distinguish TMVII from a very closely related fungus called T. interdigitale.
In addition, the skin rashes caused by TMVII are similar to those caused by T. indotineae. However, unlike TMVII, T. indotineae is often resistant to the drug terbinafine.
In a recent study published in May , researchers at New York University looked at the genetic features that allow the fungus to interfere with terbinafine. They also found that another antifungal drug called itraconazole worked better, but it could interact with other drugs and cause unwanted side effects like diarrhea.
T.indotineae was first detected in the United States last year, although retrospective analysis of patient skin samples suggests it has been in the country longer. There is some evidence that the infection can also be spread through sexual contact.
The NYU team plans to continue tracking cases of TMVII and T.indotineae in the U.S. and abroad. They stressed that while both fungi have been detected in the U.S., the level of infection in the country remains very low.
