Dermatophytosis

Definition

Dermatophytosis (also known as ringworm or tinea) is a superficial fungal infection of the skin, hair or nails.

Description

This group of superficial fungal infections is usually classified according to location on the body.

Dermatophytosis (tinea) may affect the scalp (tinea capitis), the bearded skin of the face (tinea barbae), the body (tinea corporis - mainly affecting children), the groin (tinea cruris or jock itch), the nails (tinea unguium), and the feet (tinea pedis or athlete's foot). These disorders vary from mild inflammations to acute vesicular reactions.

Although remissions and exacerbations are common, with effective treatment, the cure rate is very high. However, about 20 percent of all infected people develop chronic conditions.

Tinea lesions vary in appearance and duration.

• Tinea capitis may appear as small, spreading papules (bumps) on the scalp that may progress to inflamed, pus-filled lesions. Patchy hair loss with scaling may occur.

• Tinea barbae appears as folliculitis in the bearded area.

• Tinea corporis might include flat skin lesions at any site except the scalp, bearded skin or feet. These lesions may be dry and scaly or moist and crusty. As they enlarge, their centers heal, producing the classic ring-shaped appearance.

• Tinea cruris will include raised, sharply defined and itchy red lesions in the groin area that may extend to the buttocks, inner thighs and external genitalia.

• Tinea unguium starts at the tip of one or more nails. Fingernail infection is much less common. Inspection will reveal gradual thickening, discoloration and crumbling of the nail. Eventually, the nail may be completely destroyed.

• Tinea pedis may present with extreme itching and pain, especially while walking, because of the scaling and blisters between the toes.

• Tinea versicolor (pityriasis versicolor) is a mild, superficial infection of the skin (usually of the trunk). Lesions are asymptomatic and usually tan, pink, white or brown macules (flat patches).

Causes and Risk Factors

Tinea infections result from several different fungi. Transmission can occur directly through contact with infected lesions or indirectly through contact with contaminated articles such as shoes, towels or shower stalls. Another predisposing factor is the combination of warm weather and tight clothing, which encourages fungus growth.

Some of the fungi involved in these conditions primarily infect animals, but they may also be transmitted from animals to humans. Cats may have an infection, but may not be suspected until lesions appear on their owners.

Diagnosis

Diagnosis must rule out other possible causes of the signs and symptoms, which may include eczema, psoriasis, and contact dermatitis.

A microscopic examination of some lesion scrapings usually confirm tinea infection. This is called a KOH (potassium hydroxide) preparation. Culture of the affected area, which may take weeks, may help identify the infecting organism.

Treatment

Topical antifungal preparations should be effective in treating small, uncomplicated tinea infections located in areas other than the scalp. These include topical clotrimazole and miconazole (available over the counter) and terbinafine cream.

Sometimes, oral antifungal medication may be required if the condition is severe. Medications may include griseofulvin, itraconazole, terbinafine and fluconazole.

Tinea capitis (scalp), regardless of severity, is usually treated with oral antifungal medication, since topical antifungals do not penetrate hair follicles well. Corticosteroids may sometimes be used for the treatment of severely inflamed or potentially scarring lesions, such as scalp infections. Fungal infections involving the nails (onychomycosis) require oral treatment as well, because the dermatophyte is found deep in the nail.

Tinea versicolor may be treated with selenium sulfide lotion or ketoconazole shampoo.

Occasionally, the question arises as to whether a concurrent bacterial infection is complicating a fungal infection. This situation most commonly occurs when highly inflamed scalp lesions are draining purulent (pus) material. The lesions usually resolve with systemic (oral) antifungal and systemic corticosteroid therapy.

Prevention

The skin should be kept dry, since moist skin favors the growth of fungi. Dry the skin carefully after bathing and let it dry before dressing. Loose-fitting underwear is recommended. Socks should be changed daily. Sandals or open-toed shoes may be beneficial. Talc or other drying powders may also be helpful.

Questions to Ask Your Doctor

Are there any tests needed to diagnose the condition?

What is the cause of the condition?

What treatment will you be recommending?

Will you be prescribing any medication? What are the side effects?

How long should it take to clear up the skin infection?

Is this infection contagious? What needs to be done to prevent this from spreading?