Tinea capitis (scalp ringworm) is a fungal infection of the scalp and hair caused by different species of dermatophytes, most often those of the genera Trichophyton and Microsporum. It is the most common fungal scalp infection in the pediatric population, affecting 3%-13% of children. Most cases occur between the ages of 3 and 7 years, although it has been reported in infants and older children, and in adults as well.

Transmission is through direct contact with the infectious agents, either from humans, animals, soil, or indirectly through fomites, including hats, hairbrushes and combs, and other instruments used in hair grooming. In the United States and Great Britain, the most common causative agent is Trichophyton tonsurans. The most common agent worldwide, however, is Microsporum canis.

Endothrix infections are those in which fungal spores of the dermatophyte (arthrospores) invade the hair shaft. Trichophyton tonsurans is the most common causative species, and Trichophyton violaceum may also be responsible. Black dot tinea capitis is a common presentation of endothrix infections. Patchy alopecia and broken hairs are seen. The "black dots" refer to the ends of broken-off hairs close to the scalp.

In ectothrix infections, arthrospores do not invade the hair shaft. Microsporum species, such as M canis, and other Trichophyton species, such as Trichophyton verrucosum, cause ectothrix.

Immunocompromised patient considerations: Severe tinea capitis, along with Majocchi-like granulomas, deep ulcerated fungal infections, tinea corporis, and fungal nail involvement are characteristic of an inherited deficiency of CARD9 (caspase recruitment domain-containing protein 9), an inflammatory cascade-associated protein. The disorder is autosomal recessive and is most common in North Africa countries.

Related topics: favus, kerion