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. Most cases occur between the ages of 3 and 7 years, although tinea capitis has been reported in infants and older children, and in adults as well. It is estimated that 3%-11% of all tinea capitis cases in the world occur in adults.

Transmission is through direct contact with the infectious agents, either from affected children, animals, soil, or indirectly through fomites, including hats, hairbrushes and combs, and other instruments used in hair grooming. Some adults have tinea capitis that went untreated in childhood. Of adults, postmenopausal women are most often affected by tinea capitis.

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 Microsporum canis, and other Trichophyton species, such as Trichophyton verrucosum, cause ectothrix.

Immunocompromised patient considerations: Immunosuppression (HIV, corticosteroid therapy, renal transplantation) may predispose adults to infection. 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