Mary C. Greist, MD

The atrophic patches on the lower legs of this 47-year-old woman who has haddiabetes mellitus for over 20 years are those of necrobiosis lipoidica diabeticorum.These areas involve degeneration of collagen and elastic fibers in thelower dermis and changes in blood vessel walls. The lesions usually begin assingle or multiple elevated reddish nodules, most commonly in the pretibialarea. Over time, they expand and coalesce into distinctive brownish yellowpatches. These areas may be somewhat tender, but as they spread, theyfrequently become painless-unless they ulcerate. Because the involved skinis fragile, ulcers can form after any minor trauma.