Localized granuloma annulare. Histopathological and direct immunofluorescence study of early lesions, and the adjacent normal-looking skin of actively spreading lesions.

We studied 10 biopsies of early (< 1 week) localized granuloma annulare (LGA) lesions and 10 specimens of the normal-looking skin adjacent to actively spreading LGA lesions for signs of vasculitis, using histological and direct immunofluorescent (DIF) techniques. In the early LGA lesions, the collagen fibers showed various forms of alterations, with hyalinization and fragmentation being the most common; in half of these lesions, neutrophils and nuclear fragments in various numbers and densities were found among the altered collagen fibers. Some of the small blood vessels in the areas of granulomatous inflammation showed endothelial cell hypertrophy in four cases, and in one case also endothelial cell proliferation and luminal occlusion. In only one case, a single small blood vessel, which was situated in the center of a palisading granuloma, showed fibrinoid necrosis of its walls. The DIF study of all 20 specimens and the histological study of the 10 specimens of normal-looking adjacent skin did not reveal immune deposits in the vessels' walls, or histological evidence of vasculitis, respectively. We believe that these findings do not support a role of vasculitis in the formation of LGA lesions, but suggest that neutrophils might play a primary or secondary role in their pathogenesis.