Skin Disorders Guide

Diagnostic Hallmarks

1. Distribution: anterior lower legs
2. One or several palm-sized plaques
3. Lesional pain and tenderness

Clinical Presentation

Erythema nodosum is characterized by the presence of large ( 1- to 10-cm) nonscaling, red, painful lesions on the anterior surface of the lower legs. The smaller lesions appear as slope-shouldered nodules, whereas the larger lesions appear as flat-topped plaques. Because of this bimorphic appearance, erythema nodosum is listed with the erythematous mantles, papules, and nodules (group 7) as well as with the vascular reactions. Ulceration of the plaques does not occur.

On palpation the lesions are slightly warm and very tender. The distribution may be unilateral at first, but later in the ,ourse of the disease both legs become involved. Generally, no more than six lesions are present at anyone time. Lesions usually occur on the anterior shins or around the ankles. Lesions occasionally develop above the knee, on the thigh, or posteriorly on the calf.

Ankle and knee swelling with redness and tenderness in and round the joint is rather commonly found. Erythema nodosum occurs considerably more often in women than in men.

The rapidity of onset, together with tenderness and warmth on palpation, often suggests the presence of cellulitis. However the presence of more than a single lesion, a duration of more than several days, and the failure to respond to antibiotics usually allow for differentiation. Superficial thrombophlebitis also mimics erythema nodosum, but it is rarely if ever bilateral. Biopsy can he used to confirm a clinical diagnosis of erythema nodosum.

Course and Prognosis

Individual lesions resolve over a period of 15 to 20 days, but even as the first lesions disappear, one or more new ones begin to appear. Because of this sequential development, the entire course of the disease may last for months. Recurrent episodes, following long periods of inactivity, occur in about 5% of patients. Healing is accompanied by postinflammatory hyperpigmentation, but no permanent scarring develops.

Therapy

The discomfort of erythema nodosum is due to tissue distention, which is in turn caused by the presence of inflammation . Treatment revolves around the use of nonsteroidal anti-inflammatory agents, leg elevation, and bed rest. For patients who wish to be up and around, the use of elastic wraps or support stockings may be very helpful. In some cases, nontraditional anti-inflammatory medications such as potassium iodide, hydroxychloroquine, or dapsone may be of use. In rare instances, systemically administered steroids may be necessary . Hot soaks and topically applied medications are not efficacious.