A case of Trichophyton tonsurans infection in which incubation time can be estimated

Dear Editor, Trichophyton tonsurans is a well-known causative organism of tinea capitis in the West.1 In Japan, outbreaks of T. tonsurans infection among wrestlers and judo participants have rapidly increased since approximately 2001.2 Because judo is a national sport and a large population in Japan participates in judo, this disease poses a major public health problem for this country. We recently treated a case of T. tonsurans infection at a clinic in Tokyo that suggested that infection can spread by ordinary household contact and that allowed us to estimate the incubation time of the infection. In treating this case, we realized the pressing need to establish countermeasures against T. tonsurans infection in Japan. The patient was a 13-year-old junior-high school girl from Tokyo with no sports history. She visited our clinic on 21 September 2004, complaining of round, erythematous, scaly macules on the abdomen and left thigh. Two erythematous macules with mild itching had first appeared on the abdomen and left thigh about 1 week earlier and had gradually assumed a round shape. Medical and family history were uneventful. On the first examination, we noted an erythematous macule 2 cm in diameter with a raised border on the abdomen which was surrounded by three relatively small erythematous macules suggestive of satellite lesions. On the extensor surface of the left thigh, we observed another erythematous macule 2.5 cm in diameter with a well-defined border associated with fine scales and with a center that showed slight clearing (Fig. 1). Microscopic examination of potassium hydroxide specimens prepared from the eruptions on the abdomen and left thigh revealed many hyphae. Fungal specimens were cultured on Sabouroud’s glucose agar, and an isolate was identified as T. tonsurans using direct DNA sequencing of polymerase chain reaction amplication.3 Scalp hairs were negative for fungi by the hairbrush method. The patient was given a diagnosis of tinea corporis and treated with oral terbinafine and liranaftate cream. This case suggests that T. tonsurans can be transmitted from person to person by normal household exposure within a 4-week period, in the absence of extensive physical contact, such as judo wrestling. The patient had stayed with her mother’s family in Akita Prefecture, a northern part of the Honshu District of Japan, from 7–21 August during summer holidays. Her mother’s family consisted of three members including her 16-year-old cousin, who was a member of his high-school judo club. The cousin visited a dermatology clinic regularly for treatment of tinea corporis. His doctor had diagnosed tinea corporis on the face without performing a culture and was treating the boy only with miconazole cream. It was known that tinea was prevalent