Necrobiosis lipoidica. An immunofluorescence study.

Biopsy specimens from 12 patients with necrobiosis lipoidica (diabeticorum) were studied by direct immunofluorescent microscopy. The immunoglobulin IgM was present in blood vessel walls of involved skin from six patients, and the third component of complement (C3) was present in the blood vessel walls of involved skin from seven patients. The immunoglobulin IgA was similarly observed in two patients. In addition, IgM, C3, or fibrinogen were observed at the dermal-epidermal junction of involved skin from seven patients. Necrobiotic areas invariably contained fibrinogen. These findings suggest that an immunecomplex vasculitis may be involved in the pathogenesis of necrobiosis lipoidica.