Superficial ulcerating necrobiosis in rheumatoid arthritis. A variant of the necrobiosis lipoidica-rheumatoid nodule spectrum?

Although necrobiosis is not a precise term, it primarily refers to collagen changes found in association with the palisading granulomas seen in granuloma annulare, necrobiosis lipoidica diabeticorum (NLD), and rheumatoid nodules. While the pathogenesis of each of these conditions remains unknown, immune complex vasculitis and delayed hypersensitivity mechanisms have been postulated. Two patients are described, having "classic" rheumatoid arthritis with chronic, superficial, ulcerating, discrete lesions on their lower legs that histologically were interpreted as NLD. While the argument for a chance association of NLD and rheumatoid arthritis could be advanced, the occurrence of identical lesions in two patients with high-titer rheumatoid factor, rheumatoid nodules, and some clinical and microscopic evidence of a low-grade rheumatoid vasculitis suggests a new subset of patients with necrobiotic palisading granulomas.