Fungal infections of the scalp are extremely common in children. The diagnosis of tinea capitis should be entertained in any child in whom patches of incomplete alopecia, crusting, or scaling are found in the scalp. In previous decades, Microsporum canis and M. audouinii were the most common pathogenic fungi infecting the scalp. The latter frequently causes a discrete grayish patch of hair loss (Fig. 6-1). In most parts of the United States and in many other parts of the world, Trichophyton tonsurans is now the predominant organism causing tinea capitis. In the United States, this form of tinea capitis is seen almost exclusively in African American children. In some children, this dermatophyte causes discrete and dramatic areas of hair loss studded by the stubs of broken hairs, the so-called black-dot ringworm (Fig. 6-2). In others, there are only small and unimpressive patches of “seborrheic” scale with minimal hair loss or groups of small pustules.
Because T. tonsurans does not fluoresce, the Wood's light is no longer of use in most cases. However, diagnosis can be confirmed by the use of either potassium hydroxide preparation or fungal culture. Pictured here is an inflammatory response to infection with T. tonsurans. Children whose scalps are infected with this dermatophyte may also develop regional lymphadenopathy (Fig. 6-4), or a fine papular eruption that spreads from the face and neck to other skin surfaces (an id reaction). Attempts to treat tinea capitis with topical antifungal agents alone are doomed to failure. Oral griseofulvin is the most effective form of therapy. The use of selenium sulfide shampoo may be effective in preventing spread to classmates and siblings.
In some children, an exuberant inflammatory response to the infecting dermatophyte may occur. This boggy and tender mass is termed a kerion, a word that in Greek means a honeycomb, honey, or beeswax and is intended to describe the clinical appearance. Children with a kerion may also develop localized lymphadenopathy and fever. Although bacterial superinfection may sometimes occur, misdiagnosis of a kerion as a bacterial infection of the scalp is an all too common pitfall. The proper treatment is oral griseofulvin. In some cases, a brief course of oral prednisone may minimize scarring.
Before treatment or shortly after starting griseofulvin for tinea capitis, some patients develop a pruritic eruption that is a hypersensitivity reaction. These patients develop erythematous papules, papulovesicles, ...