Granuloma annulare.

Granuloma annular (GA) is a benign inflammatory skin disease usually localized to the distal extremities, although generalized, perforating, and subcutaneous variants have also been identified. A regular histopathologic feature is the presence of mononuclear cells, often in palisading array, around foci of altered collagen. The clinical and histologic features of each subtype of GA are discussed along with a differential diagnosis. A variety of remedies have been used to treat GA, but efficacy is hard to define in a disease in which spontaneous resolution is usual outcome. GA has not been conclusively linked either to diabetes or solar radiation. Recent data suggest a role for vascular injury or delayed-type hypersensitivity in the pathogenesis, but the cause of GA remains obscure.