Contributor: Gordon K. Klintworth
Granuloma annulare is an idiopathic skin disease of the dermis characterized by papules that are typically arranged in an annular pattern, but which may occur as isolated lesions. The extremities are often involved and affected individuals frequently have lesions over the joints and on the hands and feet. Sometimes they are generalized in distribution. Suspected predisposing factors include diabetes mellitus, trauma, and sun-exposure. The lesions consist of granulomatous inflammation with few multinucleated giant cells in and around the collagen bundles that is not associated with a vasculopathy or neovascularization. The center of the lesions contain abundant hyaluronic acid and some fibrin. Each granuloma may be palisaded or non-palisaded. When palidaded granulomas are present they resemble the rheumatoid nodule of rheumatoid arthritis. Granuloma annulare usually regresses after 1-2 years and the lesions do not leave residual depressed scars.