(See also Overview of Bacterial Skin Infections.)
Erythrasma resembles tinea or intertrigo. It most commonly affects the foot, where it manifests as superficial scaling, fissuring, and maceration typically confined to the 3rd and 4th web spaces. Erythrasma in the groin manifests as irregular but sharply marginated pink or brown patches with fine scaling. Erythrasma may also involve the axillae, submammary or abdominal folds, and perineum, particularly in obese middle-aged women and in patients with diabetes.
Erythrasma fluoresces a characteristic coral-red color under a Wood light due to production of porphyrin by the causative bacterium. Absence of hyphae in skin scrapings also distinguishes erythrasma from tinea.
Treatment of erythrasma is a single dose of oral clarithromycin 1 g. One to two treatments (80 J/cm2) of broadband red light (635 nm) have been successful in a small case series. Topical erythromycin, clindamycin, or 2% mupirocin is also effective. Recurrence is common.