A 59-year-old woman (with obesity and type 2 diabetes) presents with a 6-month history of a brown somewhat pruritic rash in both axillae (Figure 125-1A). She had been seen by multiple physicians and received many antifungal creams and topical steroids with no improvement. She had stopped wearing deodorant for fear that she was allergic to all deodorants. The rash demonstrated the classic coral red fluorescence of erythrasma (Figure 125-1B). The patient was given a prescription for oral erythromycin, and to her great delight the erythrasma cleared.
A. Erythrasma in the axilla of a 59-year-old woman with obesity and diabetes. B. Coral red fluorescence seen with a Wood's lamp. (Reproduced with permission from Richard P. Usatine, MD.)
Erythrasma is a chronic superficial bacterial skin infection that usually occurs in a skin fold.
The incidence of erythrasma is approximately 4%.1
Both sexes are equally affected.
The inguinal location is more common in men.
ETIOLOGY AND PATHOPHYSIOLOGY
Corynebacterium minutissimum, a lipophilic Gram-positive non–spore-forming rod-shaped organism, is the causative agent.
Under favorable conditions, such as heat and humidity, this organism invades and proliferates the upper one-third of the stratum corneum.
The organism produces porphyrins that result in the coral red fluorescence seen under a Wood's lamp (Figures 125-1 and 125-2).
Coral red fluorescence seen with a Wood's lamp held in the axilla of a patient with erythrasma. (Reproduced with permission from Richard P. Usatine, MD.)
Erythrasma is a sharply delineated, dry, red-brown patch with slightly scaling patches. Some lesions appear redder, whereas others have a browner color (Figures 125-3 and 125-4).
In a study of 151 patients, the reported signs and symptoms included pruritus in 81 patients (53.6%), erythema in 109 patients (72.2%), scaling in 145 patients (96%), and hyperhidrosis in 45 patients (29.8%).2
It may appear as maceration between the toes and be mistaken for tinea pedis or coexisting with tinea pedis (Figures 125-5 and 125-6).3 In a study of 182 patients with interdigital lesions in a podiatry clinic, 40% were diagnosed as having erythrasma. Diagnoses were made by Wood's lamp examination, Gram stain, and KOH preparations. The authors stated that simple and rapid diagnosis can be made with the Wood's lamp examination alone.3
Reddish brown erythrasma in the axilla of an obese woman with diabetes. (...