Vasculitis in granuloma annulare: histopathology and direct immunofluorescence

Necrotizing vasculitis

Necrotizing vasculitis is a term used to describe vessel wall necrosis due to neutrophil infiltration. Current evidence strongly suggests that these cells are responding to elaboration of chemotactic factors of the complement cascade released at the site of deposition of immune complexes in the vessel wall. The antibody is usually IgG or IgM (and rarely IgA), but the only antigens identified with even a minimum certainty are the streptococcal M protein, the hepatitis B surface antigen, and Mycobacterium tuberculosis. Vessels may be involved, leading to specific signs or symptoms, in a wide range of organs, but with those of the skin, kidney, joints, and gastrointestinal tract leading the list. Why vessels of different sizes or location become involved in individual patients is unknown. Therapy with nontoxic drugs, such as antihistamines or salicylates, is indicated when the disease is mild, but vital organ involvement may necessitate therapy with systemic corticosteroids and/or cyclophosphamide.

The ultrastructure of granuloma annulare

Nine cases of granuloma annulare at different stages of development were investigated electron microscopically. Special attention was given to collagen changes, to the cellular infiltrate, and to vascular changes. The necrobiotic changes of the collagen were: loosening of the fibers at the borders of the bundles; swelling and loss of cross-striation of the fibrils; and complete degradation of the collagen, with precipitation of mucinous and fibrin material and of glycogen. In 2 cases "cross-banded filamentous aggregations" were present. In later stages new collagen synthesis occurred. In the infiltrate, histiocytes/macrophages were seen developing into epithelioid and giant cells. In addition, numerous active lymphocytes and, at later stages, some neutrophils were found. Vascular changes consisted of endothelial swelling and duplications of the basal lamina. A perivascular infiltrate was present, but no distinct vasculitis was seen. Our results indicate that the necrobiosis of the collagen without primary vasculitis may be an initial event in granuloma annulare. A delayed hypersensitivity mechanism is discussed with regard to pathogenesis.