Skin Disorders Guide

Diagnostic Hallmarks

1. Distribution: anterior shins
2. Violaceous border
3. Central atrophy or ulceration

Clinical Presentation

Necrobiosis lipoidica diabeticorum (NLD) occurs as one or more yellow plaques on the anterior lower legs. Rarely, lesions may be found on the arms, face, and dorsal surface of the feet. Most of the plaques are 2 to 10 cm in diameter. The center of the plaque has a yellow, waxy appearance; the borders of the plaques are dusky red or violaceous. Palpation reveals a sense of firmness in the deep tissue.

Atrophy is present, and therefore, underlying veins can usually be seen more easily throughout the lesion than within the surrounding normal skin. Occasionally, the atrophic areas break down and ulcerate. The lesions are asymptomatic unless ulcerated, in which case pain may occur. Sometimes, there is overlap between the clinical appearance of granuloma annulare and NLD. Lesions of morphea often have a yellow waxy hue that can mimic that of NLD. Round and oval plaques of morphea rarely occur on the lower leg, but sometimes biopsy is required to differentiate these two diseases.

Course Prognosis

The lesions of NLD remain present for long periods of time. Usually, there is some element of slow centrifugal expansion. Approximately 60% of the patients with NLD have overt diabetes mellitus. Conversely, only about 0.5% of patients with diabetes develop these lesions.

Pathogenesis

The cause of NLD is unknown, although some clinicians believe that the plaques occur as the result of the same microangiopathy that is responsible for other complications of diabetes. There is considerable histologic similarity between NLD and the lesions of granuloma annulare and rheumatoid nodules. The significance of this observation is unknown.

Therapy

Therapy is not very effective. Some improvement may be seen following the use of topical steroids when they are used under occlusion. Intralesionally injected steroids are more effective, but there is some risk that the injected steroids will create more atrophy and increase the likelihood of ulceration. There has been some recent enthusiasm for the use of oral agents that affect blood flow (pentoxitilline) or interfere with platelet aggregation and activation (dipyridamole), but proof of efficacy has not been shown.