Erythrasma means "red spot" in Greek. It is caused by the Corynebacterium minutissimum. Exposure to heat, humidity, increased sweating, occlusive clothes, poor hygiene, obesity and immune lowering conditions like diabetes mellitus or immune suppressing medications like systemic steroids predispose individuals to erythrasma.
Signs and Symptoms of Erythrasma
Erythrasma may affect individuals of any age, though it is more common among adults than in children. The rash of erythrasma usually starts as smooth, reddish brown patches. Later the color turns brownish black with an irregular but well defined margin. The surface may become a little creased with fine scales in chronic erythrasma. The usual sites affected are the groin, armpits, chest and upper back.
Erythrasma can affect the web spaces of the fingers and toes, resulting in macerated scaly patches similar to the fungal infections. Erythrasma is more common in hot and humid temperate climates. Erythrasma has also been reported on the glans and prepuce of the penis in males.
Though usually it is localized to a particular region of the body, erythrasma can spread to involve the whole trunk in predisposed individuals in warm, humid climactic conditions.
In temperate climates erythrasma is usually asymptomatic. In tropical conditions, though, the brown patches may become irritated, especially in the groin and armpits. This results in scratching and thickening of the skin. Erythrasma affecting the skin around the anus is an uncommon cause for pruritus ani.
Very rarely, C.minutissimum has been associated with systemic diseases like recurrent boils and even endocarditis.
Untreated, erythrasma can continue for weeks to months to even years.
Diagnosis of Erythrasma
The coryneform bacteria produce a type of chemical known as coproporphyrin III which fluoresce a coral red color under Wood’s lamp light. Gram’s stain and Giemsa stain reveal the coryneform bacteria under the microscope. Potassium hydroxide preparation is useful in ruling out fungal infections, especially in toe web erythrasma.
Pityriasis versicolor, the pigmented variety, has to be ruled out in cases of erythrasma. Pityriasis versicolor is usually limited to the upper body and the rashes are small and light brown. Fungal infection of body folds show patches with central clearing and peripheral scaling and/ or vesicles. Satellite lesions are characteristic of candidiasis.
Other skin diseases to be differentiated from erythrasma are pitted keratolysis, confluent and reticulated papillomatosis, seborrheic dermatitis, acanthosis nigricans and inverse psoriasis. Healing drug rashes also may mimic erythrasma. Erythrasma can at times coexist with acanthosis nigricans.
In the toe web space, erythrasma may be difficult to differentiate from fungus or candida clinically. Wood’s lamp examination is helpful in such cases.
How to Treat Erythrasma
Benzoyl peroxide 2.5% gel, topical erythromycin, clindamycin, fusidic acid, and antifungals like clotrimazole and miconazole are all effective in treating erythrasma. In extensive cases, oral erythromycin or tetracyclines are preferred. Clarithromycin is also quite effective. Duration of treatment is usually about two to three weeks in erythrasma.
How to Prevent Relapses in Erythrasma
Prevention of relapses of erythrasma mainly depends upon avoidance of predisposing factors. Treating active disease early with oral antibiotics usually helps prevent early recurrences of erythrasma. Use of benzoyl peroxide bars and other antiseptic soaps like povidone iodine helps prevent erythrasma relapses as does regular use of antiseptic or antifungal powders in the body folds.
Sources:
- Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology, Fifth Ed, 2005
- Rook’s Textbook of Dermatology, 7th Edition, 2004
Disclaimer
The information given in this article is for educational purposes only so that patients are aware of the options available. No diagnosis should be made or treatment undertaken without first consulting your doctor. If you do so, the author or Suite101 will not be responsible for any consequences. The images provided are for illustration purpose only.
Hanish Babu - Dr.Hanish Babu, MD is a dermatologist and a feature writer on Suite101.com with more than 200 articles related to skin diseases on the ...
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