Boy Wrestles With Scalp Problem

ANSWER
The correct answer is all of the above (choice “e”). This particular form of tinea capitis is called black dot tinea capitis (BDTC), a somewhat unusual dermatophytosis (superficial fungal infection) that mostly affects children. The causative organisms are anthropophilic—that is, acquired from human sources, such as other children, during activities that involve skin-to-skin contact (eg, sports).

The vast majority of these organisms are from the Trichophyton family, such as T tonsurans or T violaceum. They invade the hair shaft itself, leaving the hard covering (the cuticle) intact. The black dots represent the tips of broken-off hairs, themselves full of fungal elements, seen in the photomicrograph. The term endothrix is given to this kind of fungal infection, in which the organisms are contained within the hair shaft, which, as a result, becomes brittle and breaks off. This is a relatively common type of infection.

A more unusual form of tinea capitis is caused by zoophilic organisms, such as Microsporum canis (from dogs and cats), Microsporum gypseum (pigs or cows), or T equinum (horses). These infect the external surface of the hair shaft, breaking down the cuticle. This allows for identification of the infection by Wood’s lamp, which causes the affected area to turn a yellowish color. These infections also tend to provoke a more brisk inflammatory response in the victim and are more difficult to treat.

Diagnosis can be made from a combination of clinical findings, KOH prep (as in this patient), and/or fungal culture.

Treatment can entail griseofulvin or terbinafine; the case patient was treated with a two-month course of the latter (125 mg/d). Topical treatment is of limited usefulness.