Granuloma annulare is a chronic, harmless skin disorder in which small, firm, raised bumps appear and spread out to form a ring with normal or slightly sunken skin in the center.
The cause of granuloma annulare is not clear, but doctors suspect it is the result of an immune reaction. Having granuloma annulare does not mean that another disorder is present.
In a few people who have granuloma annulare, certain factors may cause clusters of granuloma annulare bumps to erupt. Such factors include exposure to sunlight, insect bites, skin testing for tuberculosis, bacille Calmette-Guérin vaccination, injury, infection with Borrelia bacteria, and viral infections.
Granuloma annulare occurs twice as often in women as in men.
The bumps are usually red but may be slightly bluish, yellowish tan, or skin-colored, and a person may have one bump or several. The bumps may be tender but usually cause no pain or itching. They most often form on the feet, legs, hands, or fingers of children and adults. The bumps often expand outwardly to form rings. The center of each ring may be clear or be slightly sunken and sometimes pale or light brown. In some people, the rings become widespread.
Doctors usually diagnose granuloma annulare by its appearance.
A sample of skin may be removed and examined under a microscope (called a skin biopsy) to confirm the diagnosis.
Most often, granuloma annulare heals without any treatment, so people who have no symptoms usually require no treatment.
Corticosteroid creams under waterproof bandages, surgical tape saturated with a corticosteroid, or injected corticosteroids may help clear up the rash. Alternatively, tacrolimus may be applied to the skin.
People with large affected areas often benefit from treatment that combines phototherapy (exposure to ultraviolet light—see Phototherapy: Using Ultraviolet Light to Treat Skin Disorders) with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light). This treatment is called psoralen plus ultraviolet A (PUVA) therapy.
Isotretinoin, dapsone, and cyclosporine may be effective if rings are widespread.
Other possible therapies include infliximab, adalimumab, and different types of lasers.