Click here to view next page of this article

Ringworm and Dermatophyte Infections

Dermatophytes constitute a group of about 40 fungal species that cause superficial infections called dermatophytoses, ringworm, or tinea ringworm.

Tinea capitis

Tinea capitis presents as inflammation with hair breakage and loss. Inflammatory changes can range from minimal scaling and redness that resembles mild seborrhea to tenderness, redness, edema, purulence, and hair loss (kerion).

A hypersensitivity reaction to fungal antigen can develop, called a dermatophytid or "id" reaction. Id reactions can present with either a dermatitis that includes redness, superficial edema involving the epidermis, and scaling or with a "pityriasis rosea-like" reaction that involves red, scaly papules and ovoid plaques on the face, neck, trunk.

Tinea corporis ( ring worm) and tinea cruris

Dermatophyte infection of the body surface is termed tinea corporis. Tinea cruris describes infection of the upper thigh and inguinal area. Examination reveals red, scaly papules and small plaques.

Tinea pedis and tinea manuum

Tinea pedis infection is often interdigital and is induced by the warmth and moisture of wearing shoes. The web spaces become red and scaly. Fungal infection frequently spreads to involve the soles of the feet or the palms, with dry scale and minimal redness. Scaling extends to the side of the foot or hand.

Onychomycosis ( tinea unguium)

Dermatophyte infection of the nail plate is referred to as onychomycosis, characterized by dystrophy of the nail, discoloration, ridging, thickening, fragility, breakage, accumulation of debris beneath the distal aspect of the nail and little or no inflammation.

Oral treatment usually is required to clear infection, but recurrence is very common.

Diagnosis

Potassium hydroxide (KOH) examination of scale, hair, or nail is the most rapid diagnostic method. A sample of scale, hair, or nail from a possibly infected area is placed on a glass slide, covered with a few drops of 30% KOH, and gently heated. The specimen is examined for spores and/or fungal hyphae.

Fungal culture of scale and affected hair or nail can be accomplished by incubation at room temperature for 2 to 3 weeks.

Treatment

Oral griseofulvin is effective and safe for treatment of tinea capitis in children. However, its erratic oral absorption necessitates doses of about 20 mg/kg per day of the liquid preparation, always administered with a fatty meal or beverage (such as milk). Ultramicrosize griseofulvin can be administered.

Itraconazole ( Sporanox) is effective and can be given orally at 3 to 5 mg/kg per day for 4 to 6 weeks.

Terbinafine ( Lamisil) orally at 3 to 6 mg/kg per day for 4 to 6 weeks.

Topical antifungals can be used once to twice daily to clear infections other than tinea capitis and onychomycosis. Newer, more potent topical agents with once-daily dosing.

Hydrocortisone 1% or 2.5% can be added to antifungal therapy to reduce inflammation. Affected areas should be kept as cool and as dry.