Collagen-elastic tissue changes and vascular involvement in granuloma annulare: a review of 35 cases

The pathogenesis of granuloma annulare (GA) is unclear. Collagen fiber degeneration is commonly reported, and there are several conflicting studies on elastic fiber and vascular changes associated with GA. In this study, we aimed to evaluate histopathologic characteristics, collagen and elastic tissue changes and vascular changes in GA.

Clinical records of 35 GA patients were examined alongside serial sections of 38 biopsy specimens from these patients. New sections of biopsy tissue were stained with hematoxylin and eosin, Verhoeff-van Gieson or Alcian blue and then evaluated.

Four different histopathologic patterns were observed: interstitial (57.9%), palisadic granulomatous (26.3%), sarcoidal granulomatous (5.3%) and mixed (10.5%). Dermal mucin deposition was determined in 84.2% of specimens. Solar elastosis was observed in only seven specimens, and elastophagocytosis was observed in only two specimens. Collagen and elastic tissue damages were consistent findings in all biopsy specimens. Fibrin thrombi and vasculitic changes were not found in any of the specimens from this patient group.

Elastic and collagen fiber damage are the main accompanying features of GA, which may develop from delayed-type hypersensitivity. Vasculitis does not appear to be a major causative process. Sun exposure also seems to have no major effect on the formation of GA but can be one of the stimulants or predisposing factors.