Etiology of granuloma annulare is unclear, but proposed mechanisms include cell-mediated immunity (type IV), immune complex vasculitis, and an abnormality of tissue monocytes. Many diseases, infections, drugs, and environmental factors have been reported in patients with granuloma annulare, but any associations are still unclear. The condition is twice as prevalent among women.
Lesions are erythematous, yellowish tan, bluish, or the color of the surrounding skin; one or more lesions may occur, most often on dorsal feet, legs, hands, or fingers. They are usually asymptomatic but may occasionally be tender. The lesions often expand or join to form rings. The center of each ring may be clear or be slightly depressed and sometimes pale or light brown. In some cases, lesions may become generalized and widespread.
Diagnosis of granuloma annulare is usually clinical but can be confirmed by skin biopsy. Unlike tinea corporis (which can cause raised annular lesions with central clearing), granuloma annulare typically has no scale and does not itch.
Usually no treatment is necessary; spontaneous resolution is common but may take years. For patients with more widespread or bothersome lesions, quicker resolution may be desired.
For localized lesions, high-strength topical or intralesional corticosteroids, topical tacrolimus, cryotherapy, and various forms of phototherapy may be used.
For widespread lesions, hydroxychloroquine, isotretinoin, dapsone, and cyclosporine have also been reported to be successful treatments.
Tumor necrosis factor (TNF)-alpha inhibitor therapy has been reported to be effective in treating granuloma annulare but has also been reported as a potential inciting factor in some patients.