Review Question - QID 108613

This patient is presenting with a dry scaly patch that has developed into an area of hair loss, and a positive KOH test suggesting a diagnosis of tinea capitis. This is best managed with oral anti-fungals such as itraconazole, terbinafine, or less frequently griseofulvin.

Tinea capitis is a subacute or chronic dermatophyte infection of the scalp. It is most common in children between 3-8 years old. It may be spread by animals such as cats and dogs, thus multiple children in a home with pets may be affected. Clinically, it presents as a scaly patch and patchy alopecia. The lesion will often have an erythematous, “active border,” and within the patch the hairs will break off at the scalp surface causing a residual black dot. Tinea capitis may also appear as favus, or yellow crusts and matted hair with smooth areas of hair loss. Post-auricular lymphadenopathy can be present. Tinea capitis must be treated with systemic anti-fungal agents, such as oral itraconazole, terbinafine, or griseofulvin, because topical agents do not penetrate the hair shaft. Treatment for tinea capitis with oral itraconazole or terbinafine is for 4 to 6 weeks while oral griseofulvin requires a longer duration of therapy.

Figure A shows a KOH preparation of skin scrapings from a patient with tinea capitis. The characteristic segmented hyphae are seen. Illustration A shows the characteristic presentation of tinea capitis including a scaly plaque and hair loss with a black dot pattern where the hair is broken off at the base. Illustration B shows the features of seborrheic dermatitis including localized red, scaly, pruritic patches on the scalp, ears, eyebrows, and nose. Illustration C shows a scaly, erythematous, ovoid, herald patch on the torso, which is characteristic of pityriasis rosea. Illustration D shows the classic Christmas tree pattern of pityriasis rosea, made up of multiple, small, red, ovoid, scaly lesions on the back. Illustration E shows head lice with characteristic 1 mm nits that attach to hair shaft and a live louse.

Incorrect Answers:
Answer 2: Selenium sulfide shampoo has been shown to decrease tinea capitis transmission, but treatment of tinea capitis requires oral anti-fungals. Selenium sulfide shampoo can also be used to treat seborrheic dermatitis (or "cradle cap" in an infant), which is caused by the fungus Malassezia furfur and can commonly be misdiagnosed as tinea capitis. Seborrheic dermatitis is characterized by localized red, scaly, pruritic patches on the scalp, ears, eyebrows, and nose (Illustration B).

Answer 3: Topical corticosteroids cannot be used to treat tinea capitis, but is part of supportive treatment for pityriasis rosea which can present on the scalp. Pityriasis rosea is an acute, self-limited, skin eruption, which classically begins with a large circular or oval patch (herald patch, as shown in Illustration C) on the trunk or back, followed by smaller ovoid lesions classically arranged in a Christmas tree pattern (Illustration D). Topical corticosteroids can also be used to treat atopic dermatitis or eczema, which can commonly be seen in children with a significant family history of atopy and can be worsened by allergies (such as to a cat).

Answer 4: Topical antifungals, unlike for other superficial dermatophyte infections, cannot be used to treat tinea capitis. Tinea capitis must be treated with systemic antifungal agents because topical agents do not penetrate the hair shaft. Topical antifungals may be used as adjuvants to prevent transmission.

Answer 5: Pyrethrin 5% shampoo is used to treat pediculosis capitis, or head lice. Head lice most commonly occurs in school age children or those in crowded living conditions. The egg cases, or nits, appear as 1 mm white bulbs attached to the hair shaft (Illustration E). Mechanical removal of nits by fine-toothed comb is also an important part of treatment.

Bullet Summary:
Tinea capitis often presents with a scaly, erythematous patch on the scalp that may develop into alopecia with residual black dots. Treatment consists of oral terbinafine, itraconazole, or griseofulvin. Topical anti-fungals cannot be used to treat tinea capitis, but may be used to prevent transmission.