Tinea capitis is a fungal infection of the scalp with invasion of the hair shafts by a dermatophyte. Dermatophytes causing tinea capitis include Microsporum canis, M. audouinii, Trichophyton tonsurans and, less commonly, other organisms.
A patch of alopecia is noted. Hairs are broken at the surface. The hair stumps, black dots, are highly suggestive of a fungus infection. There may be follicular pustules also evident, most typically at the edge of the lesion.
Wood's light examination can show typical fluorescence. Examination of extracted hairs under potassium hydroxide can show fungi. Scrapings of hairs and pustules can show fungi.
An inflammatory nodular lesion, called a kerion, can develop. Crusting, matting of adjacent hairs and pustular discharge is common. Kerions indicate an intense host immune response typically against Trichophyton verrucosum or T. mentagrophytes.
Favus is an infection with T. schoenleinii which shows characteristic yellow-white crusts known as scutula. Such crusting with pus under the crusts can occur diffusely over the scalp.
Joke and Humors
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