Photo Rounds

Geometric rash on arms and legs

A 54-year-old woman presented to her family physician (FP) with an unusual geometric rash that had developed on her arms and legs over the previous 3 months. She denied any itching or pain. She was being treated for diabetes and had been taking metformin regularly for the past 2 years without any adverse effects. Her diabetes was well-controlled, and she mentioned no other health concerns at the visit.

What’s your diagnosis?


Geometric rash on arms and legs

The FP thought this looked like granuloma annulare (GA) but had never seen so many lesions on a patient. Some lesions were not round (more oval or elongated), while others were not completely enclosed geometric shapes (with breaks in the multiple ring patterns). However, all of the lesions were slightly raised with erythema and no scale. (The FP also considered tinea corporis, but ruled it out because there was no scale.)

He consulted some Internet resources and was convinced that this was disseminated GA. The greatest risk factor for this somewhat mysterious disease of unknown origin is female gender. It is also often associated with diabetes, but diabetes is not the cause.

Although intralesional steroids work when treating disseminated GA, this approach is not realistic for widespread disease. A number of options have been studied and reported in small series or case reports. The FP presented various options to the patient, and together they decided to try pentoxifylline 400 mg 3 times daily for systemic treatment. Pentoxifylline is approved for claudication and has few adverse effects or risks. While this treatment is off-label for GA, there are no FDA approved treatments.

During a follow-up visit 1 month later, the number of lesions had been reduced by half. The FP continued treating the patient with pentoxifylline with the hope of achieving full resolution.

Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Mauskar M, Usatine R. Granuloma annulare. In: Usatine R, Smith M, Mayeaux EJ, et al. Color Atlas and Synopsis of Family Medicine. 3rd ed. New York, NY: McGraw-Hill; 2019:1141-1146.

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