Erythrasma

Definition/diagnostic criteria Erythrasma is a chronic superficial infection of the intertriginous areas of the skin caused primarily by the bacterium Corynebacterium minutissimum. It typically presents as slowly enlarging pink or brown patches, most commonly affecting the toe clefts, inner thighs, groin, axillae,  and the intergluteal and submammary flexures​​.

Epidemiology Erythrasma occurs in various climates but is more prevalent in warm environments. It can affect any age group, though it is more common in adults than children. The condition is often found in diabetic patients and may have a higher prevalence in obese, middle-aged individuals, particularly those of black descent​​.

Diagnosis
Clinical features: Erythrasma typically appears as well-demarcated patches that are slowly enlarging. These patches are smooth and pink-red or brown in new lesions and become brown with a wrinkled, scaly appearance in older lesions. The most commonly affected site is the toe clefts, but significant infections can occur on the inner thighs, groins, axillae, and in intergluteal and submammary areas. The condition is usually asymptomatic, though it may occasionally be itchy​​.

Investigations: The diagnosis of erythrasma is predominantly clinical. However, when necessary, it can be confirmed by a swab or scraping sent for microscopy and culture. Under Wood’s light (longwave ultraviolet radiation), erythrasma lesions fluoresce a coral-pink color due to porphyrins released by the bacteria, helping the diagnosis​​​​.

Treatment The standard treatment for erythrasma involves the application of topical antifungal agents like clotrimazole or miconazole twice daily for two weeks. For more extensive cases or those not responding to topical treatment, oral options like a single dose of clarithromycin (1 g), a short course of erythromycin, or a tetracycline may be effective.

In recurrent cases, weight loss advice, keeping the skin dry, and the use of an antiseptic wash can be beneficial​​.

Prognosis The prognosis for erythrasma is generally good, especially when promptly and adequately treated. Topical treatments are effective in most cases, leading to resolution of the infection. However, recurrence can occur, particularly in individuals with predisposing factors such as obesity or diabetes. Maintaining skin dryness and hygiene can help prevent recurrences.