Dermatophytosis

A common fungal infection of the stratum corneum of the skin, hair, or nails by a dermatophyte.

Other names

• Ringworm
• Tinea
• Athlete's foot (location specific)

Clinical features

It is characterized by itching, inflammation, redness of the skin, small papular vesicles, central clearing, fissures, scaling, and/or hair loss in the affected area.

Cause

Ringworm is a common skin infection that is caused by fungus.

Areas of the body that can be affected by ringworm include:

• Feet (tinea pedis, commonly called “athlete’s foot”)
• Groin, inner thighs, or buttocks (tinea cruris, commonly called “jock itch”)
• Scalp (tinea capitis)
• Beard (tinea barbae)
• Hands (tinea manuum)
• Toenails or fingernails (tinea unguium, also called “onychomycosis”) Click here for more information about fungal nail infections.
• Other parts of the body such as arms or legs (tinea corporis)

Fungal species

• Approximately 40 different species of fungi can cause ringworm;
• The scientific names for the types of fungi that cause ringworm are Trichophyton, Microsporum, and Epidermophyton.

Diagnosis

Physical examination

• A thorough history and physical examination is often sufficient to diagnose tinea.
• The classic lesion is an erythematous, raised, scaly ring with central clearing.
• Multiple lesions may be present.

Microscopy

• Potassium hydroxide (KOH) stain a commonly-used method for diagnosing tinea because it is inexpensive, easy to perform, and has high sensitivity.
• Scrapings from the lesion(s) are placed in a drop of KOH and examined under a microscope for the presence of fungal hyphae.

Ultraviolet light (Wood’s lamp)

• Normally, ultraviolet light is not useful in the diagnosis of tinea with the exception of two species – Microsporum canis and audouinii.
• Although both species fluoresce blue-green under a Wood’s lamp, both species are uncommon causes of tinea infections.
• A Wood’s lamp may be useful to differentiate between erythrasma caused by Corynebacterium minutissimum (which fouresces coal-red) from tinea cruris, which is non-fluorescent.

Culture

• Fungal culture can be performed as a confirmatory test if results from a KOH stain are inconclusive.
• Hair and/or scrapings extracted from affected areas are placed on Sabouraud’s medium.
• Fungal culture is more specific than KOH stain, but it can take up to three weeks to become positive.

Treatment

• Some forms of ringworm can be treated with non-prescription (“over-the-counter”) antifungal creams, lotions, or powders.
• Other forms of ringworm need treatment with prescription antifungal medications depending on the type of fungus.

Tinea pedis: Athlete’s foot can usually be treated with over-the-counter topical antifungal products;

• terbinafine appears to be most effective, but other agents can also be used.
• Chronic or extensive tinea pedis may require treatment with oral antifungal agents such as terbinafine, itraconazole, or fluconazole.
• In addition, chronic tinea pedis may require adjunctive therapy such as foot powder or talcum powder to prevent skin maceration.

Tinea capitis: Treatment with systemic antifungal medication is required, as topical antifungal products are ineffective for treatment of tinea capitis.

• Many experts consider griseofulvin to be the drug of choice.
• Terbinafine is also FDA-approved for the treatment of tinea capitis in patients four years of age and older.
• Itraconazole and fluconazole have been shown to be safe and effective, but are not FDA-approved for this indication.
• Selenium sulfide shampoos can be used as adjunctive therapy.

Tinea corporis/Tinea cruris: Tinea corporis and tinea cruris can usually be treated with over-the-counter antifungal products.

• Patients who have tinea cruris should be advised to keep the groin area clean and dry and to wear cotton underwear.
• Persons who have extensive or recurrent infections may require systemic antifungal therapy.

Steroids should not be used

• People who have ringworm don’t always know what’s causing their rash, and people sometimes apply over-the-counter creams or ointments containing corticosteroids (or “steroids” for short) to their rash.
• Steroid creams don’t kill the fungus that causes ringworm.
• Steroid creams also can make ringworm worse because they weaken the skin’s defenses.
• In rare cases, steroid creams allow the fungus that causes ringworm to invade deeper into the skin and cause a more serious condition.
• Steroid creams can make ringworm infections spread to cover more of the body.

An Emerging International Problem in India

• Dermatologists in India have reported severe steroid-modified tinea associated with use of over-the-counter mid- to high-potency topical corticosteroids, which are commonly sold as fixed-dose combinations with an antifungal medication and one or two antibacterial medications.
• In India, a dermatophyte species often identified as Trichophyton mentagrophytes has been reported as the cause of these breakthrough infections.

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  Athlete's foot

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