Photo Rounds

Itchy rash in axillae

A 42-year-old overweight woman with type 2 diabetes sought care from her family physician (FP) for a brown itchy rash in both axillae. She’d had it for 6 months and had been seen by several physicians. She’d tried many antifungal creams, including hydrocortisone, but her condition hadn’t improved. She’d stopped wearing deodorant for fear that she was allergic to it. The FP noted brown scaling patches in both axillae.

What's your diagnosis?


The FP diagnosed erythrasma, a chronic superficial bacterial skin infection found in the intertriginous areas—especially the axilla and the groin. Patches of erythrasma can also be found in the interspaces of the toes, intergluteal cleft, perianal skin, and inframammary area.

The causative agent is Corynebacterium minutissimum, a lipophilic Gram-positive non–spore-forming rod-shaped organism. In hot and humid conditions, this organism can invade and proliferate in the upper one-third of the stratum corneum. The organism produces porphyrins that result in coral-red fluorescence under a Wood’s lamp. Washing the area before examination, however, may eliminate the fluorescence.

Patients with erythrasma will present with well-demarcated, dry, red-brown patches that are slightly scaly in places. Some lesions appear redder in color whereas others appear browner—especially in patients with darker skin. Some patients don’t find the lesions bothersome, while others will complain of itching and burning. Risk factors for erythrasma include a warm climate, diabetes mellitus, immunocompromised status, obesity, hyperhidrosis, and poor hygiene.

Although the bacteria respond to a variety of antibacterial agents, the treatment of choice is oral erythromycin 250 mg 4 times a day for 14 days. Topical erythromycin 2% solution applied twice daily is an alternative for mild cases. Oral erythromycin shows cure rates as high as 100%. For treatment and prophylaxis of more severe cases, topical clindamycin may be added once daily during the course of oral erythromycin therapy and for 2 weeks after physical clearance of the lesions.

In this case, the FP prescribed oral erythromycin and the patient’s erythrasma cleared completely.

Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Allred A, Usatine R, Smith M. Erythrasma. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013:689-692.

To learn more about the Color Atlas of Family Medicine, see:

You can now get the second edition of the Color Atlas of Family Medicine as an app by clicking on this link:

Next Article: