Erythrasma is a superficial bacterial infection of the stratum corneum caused by Corynebacterium minutissimum. It presents as well-demarcated, brownish-red patches in intertriginous areas with fine scale and minimal symptoms. Wood’s lamp reveals coral-red fluorescence due to coproporphyrin III, aiding diagnosis. Management includes topical or oral macrolides, hygiene measures, and mitigation of predisposing factors such as occlusion, hyperhidrosis, and diabetes.
Epidemiology and Risk Factors
- More common in adults, warm/humid climates, and in those with diabetes or obesity.
- Predilection for intertriginous zones: toe webs, groin, axillae, inframammary folds.
- Coexists with tinea pedis and candidiasis; consider polymicrobial intertrigo.
Clinical Features
- Sharply demarcated, reddish-brown to copper patches/plaques with fine powdery scale; often asymptomatic or mildly pruritic.
- Toe web involvement can mimic tinea pedis; maceration may be present.
Differential Diagnosis
- Tinea pedis/cruris (KOH positive for hyphae), candidal intertrigo (satellite pustules), inverse psoriasis, seborrheic dermatitis, intertrigo with gram-negative overgrowth, contact dermatitis.
Diagnosis
- Wood’s lamp: coral-red fluorescence (coproporphyrin III). Note: recent bathing or antibacterial soaps can reduce fluorescence.
- KOH prep to rule out dermatophyte/candida coinfection.
- Gram stain/culture rarely needed; shows gram-positive rods if obtained.
Management
- Topical therapy (first-line for localized disease)
- Clindamycin 1% solution/gel bid for 1–2 weeks.
- Erythromycin 2% solution/gel bid for 1–2 weeks.
- Benzoyl peroxide washes (2.5–5%) daily as adjunct to reduce bacterial load.
- Fusidic acid (where available) is effective.
- Oral therapy (extensive, recalcitrant, or interdigital/plantar involvement)
- Erythromycin 250 mg qid or 500 mg bid for 7–14 days.
- Clarithromycin 1 g single dose has reported efficacy; alternatives: azithromycin 1 g single dose or 500 mg daily × 3 days (regional practices vary).
- Adjunctive measures
- Keep areas dry; absorbent powders (zeolite/talc-free), antiperspirants for hyperhidrosis.
- Weight management, loose breathable clothing, glycemic control in diabetes.
- Treat concomitant tinea/candida if present.
- Recurrence prevention
- Intermittent use of benzoyl peroxide wash or topical clindamycin/erythromycin 1–2 times weekly in prone individuals.
- Foot hygiene for toe web disease; change socks, ventilated footwear.
References (recent guidelines and key reviews)
- Intertriginous infections and erythrasma management overviews, 2021–2024.
- Studies on macrolide regimens and single-dose clarithromycin/azithromycin, 2021–2023.
- Role of Wood’s lamp in diagnosis, 2022–2024.