Erythrasma groin_0112 Derm Dx 4
A 65-year-old obese male with a history of hypertension and hyperlipidemia complains of light-brown patches, accompanied by itching in the groin that has been present for four months. The patient’s current medications include atorvastatin (Lipitor) and hydrochlorothiazide. He lives by himself and reports drinking about four beers a day. He has not had sexual relations in five years.
Physical exam reveals an overweight white male in no acute distress. An unpleasant odor is noted upon groin examination. Skin exam demonstrates symmetric, light brown, slightly wrinkled patches in the inguinal folds. Bright, coral-red fluorescence is observed when the patient is examined with a Wood’s lamp. The skin between the patient’s toes is mildly macerated. What’s your diagnosis?
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Erythrasma is a chronic and mild superficial skin infection caused by the diptheroid Corynebacterium minutissimum, a gram-positive rod-shaped bacteria. Obesity, diabetes, elderly age, poor hygiene, humid environment and immunosupression are predisposing factors.
C. minutissimum growth is favorable in moist and occluded intertriginous areas such as the axilla, groin, and inframammary and intergluteal folds. The lesions appear as red to brown well-demarcated patches, often with fine scale and a wrinkled appearance. Intertriginous infections are frequently asymptomatic, or may be associated with an itching or burning sensation. C. minutissimum can also cause chronic asymptomatic maceration in the toe web spaces.
Erythrasma lesions may be asymptomatic to moderately pruritic. When examined with a fluorescent Wood’s lamp (which fluoresces at a wavelength of 365 nM), bright coral red fluorescence is appreciated. This fluorescence is due to the chemical coproporphyrin III, which C. minutissimum produces.
Erythrasma diagnosis is made from clinical appearance and Wood’s lamp examination. Differential diagnoses for intertriginous erythrasma include tinea, candidiasis, inverse psoriasis and lichen simplex chronicus.
Erythrasma treatment includes improved hygiene, washing with antibacterial soaps and various topical therapies, including erythromycin or clindamycin solutions, which are rapidly effective. For extensive or recalcitrant infections, oral erythromycin four times a day for one week has been reported effective.
1. Bolognia J, Jorizzo JL, Rapini RP. “Chapter 73: Bacterial Diseases.” Dermatology. 2008; St. Louis, Mo.: Mosby/Elsevier.
2. James WD, Berger TG, Elston DM, et al. “Chapter 14:Bacterial Infections.” Andrews’ Diseases of the Skin: Clinical Dermatology. 2006; Philadelphia: Saunders Elsevier.