- Ringworm - CDC/ Dr. Lucille K. Georg
Tinea corporis is a superficial fungal skin infection, which has a raised reddish margin surrounding an inner area which may look healthy or may be somewhat scaly, and is sometimes called “ringworm”. The reason for the name is obvious when one looks at the lesion. To people without the knowledge that is now available through simple microscopy, the appearance of the lesion does resemble a worm under the skin. However, no worms are involved.
Cause of Tinea Corporis
The fungi most frequently involved in tinea corporis are: Trichophyton rubrum (causes nearly half of all cases of tinea corporis); Trichophyton tonsurans (causes most cases of tinea capitis – fungal infection of the scalp); and Microsporum canis (third most common cause of tinea corporis).
As a fungal infection of a superficial layer of the body, tinea is spread by physical contact with another person who has the infection, or with an animal or an inanimate object (as in sports facilities, showers, and so on). The incubation period is one to three weeks.
Signs and Symptoms of Tinea Corporis
The fungi may affect the skin on any part of the body. They do not affect the mucosa in the mouth or in the vagina. Fungi do especially well in hot, sweaty areas like the groin (causing jock itch), under the breasts, under the arms, and in any skin folds.
Generally, the infection will present with an itchy skin lesion, which usually begins as a scaly, red plaque. As this enlarges, the outer margin is raised, as this is where the fungus is actively proliferating, and the central area settles to look fairly normal. Often, more than one lesion will be in close proximity and may overlap, resulting in an irregular margin. The lesions may become very large, occupying a substantial portion of the torso. Because of inflammation, patients may develop crusting, and little blister-like lesions on the outer active margin.
People who are HIV positive or immunocompromised for any other reason may have pain and burning in the lesion. If a patient is on cortisone, tinea corporis will present atypically (tinea incognito).
If the infection is on the scalp, it will present with itching, and scaling, which may simply look like a worsening of normal dandruff. But it will be in a confined area, where a bald patch will develop. This is known as tinea capitis.
Athlete’s foot (tinea pedis) is a fungal infection of the skin on the feet. It develops as a result of the feet being hot and sweaty in footwear, or picking up the fungus in communal showers.
Differential Diagnosis of an Itchy, Scaly Skin Rash
Some of the more common skin conditions which need to be considered when diagnosing tinea corporis include:
- tinea versicolor
- seborrhoeic dermatitis
- psoriasis – annular and plaque
- atopic dermatitis
- nummular dermatitis
- cutaneous candidiasis
- erythema multiforme
- impetigo
- lupus erythematosus, subacute cutaneous
- granuloma annulare
- pityriasis rosea
- syphilis.
Treatment of Tinea Corporis
Treatment is either topical or systemic. Most cases are sufficiently localized to respond well to simple topical treatment. These are generally available over the counter in pharmacies without requiring a doctor’s prescription. The result is that most people never need to see a doctor about their fungal infections, unless they do not treat the infection correctly. The most frequent mistake people make that results in a visit to the doctor about their tinea corporis is stopping their treatment too soon.
Topical treatments of tinea corporis include azoles, which weaken the fungus, preventing it from reproducing and slowly killing it. There are also allylamines, which cause rapid cell death. These are an extremely effective treatment. Topical corticosteroids may be added to the topical agent to give more rapid relief if there are severe inflammatory symptoms. One doesn’t want to use cortisone for too long, however, because of side effects.
Systemic, usually oral, treatment is used in cases of extensive tinea corporis; cases which are resistant to topical treatment; patients who are immunocompromised; and in patients who have fungal infections extending to the nails and scalp as well. In some severely immunocompromised patients, intravenous antifungal treatment may be needed.The earliest of the systemic treatments was griseofulvin. Newer and more frequently used drugs are the systemically used azoles: ketaconazole, fluconazole and itraconazole. Terbafine is another treatment.
Tinea corporis may recur if treatment is stopped too soon; either the fungus has not been killed off or it is resistant. Another possibility is that there may be a reservoir of infection on the patient that has not been adequately treated. These take a lot longer to treat fully. Prevention involves simple hygiene. Avoid physical contact with a person or a pet known to have a fungal infection. Don’t share items like towels, hats and shoes. In hot weather, or when exercising, wear loose-fitting cotton fabrics.
Reference
Lesher Jr JL, Dec 2009, Tinea Corporis (accessed 15 May 2010).
Sally Powrie - I am a wife, mother of 5, mother-in-law of 2, grandmother of 2, general practitioner of more than 20 years standing, and for the last 4 ...
