Eosinophils are not a clue to the pathogenesis of granuloma annulare

Eosinophils are variably present in biopsy specimens of granuloma annulare (GA). A retrospective study of 77 biopsy specimens from 73 patients with GA was performed to quantitate eosinophils and correlate the findings with both histologic and clinical features. Specimens were divided into absent, low (10 > x > or = 1 eosinophils per 3 sections), and high (x > or = 10 eosinophils per 3 sections) eosinophil groups and evaluated for eight histologic and 11 clinical features. Eosinophils were identified in 66% (51/77) of biopsy specimens, with 51.9% (40/77) and 14.3% (11/77) in the low and high eosinophil groups, respectively. Clinically, patients in the high eosinophil group were found to be significantly younger with a propensity towards nonannular, localized disease. These patients also did not have diabetes or use systemic medications. Histologically, the presence of eosinophils was strongly associated with palisaded architectural pattern and the presence of necrobiosis. Eosinophils were not present in areas of necrobiosis but were found predominantly perivascularly. A moderate to marked lymphocytic infiltrate at the periphery of the granulomas and reactive vessel changes were common in all three groups, but vasculitis was not identified. In summary, this study showed eosinophils to be commonly present in GA but was unable to correlate their presence with specific clinical or histologic features supportive of an allergic precipitant. A cell-mediated immune mechanism is likely involved in GA, with eosinophils recruited nonspecifically by mediators released during granuloma formation.