Granuloma annulare (GA) is skin disorder that most often causes a rash with red bumps (erythematous papules) arranged in a circle or ring pattern (annular). GA is not contagious and is not cancerous. The rash may be localized or generalized. Localized GA is the most common form of GA (75% of the cases) and usually affects the forearms, hands, or feet. The generalized form of GA (15% of cases) presents with numerous erythematous papules that form larger, slightly raised patches (plaques) anywhere on the body, including the palms of hands and soles of feet. The plaques may or may not be in the ring pattern and can vary in color. Less common forms of GA include subcutaneous, perforating, and patch variants.

The underlying cause of GA is unknown, but there are several factors that may trigger the disorder, including injury to the skin, viral infections, and certain medications and medical diseases. However, most cases of GA develop in healthy people. Some researchers propose unknown genetic factors may increase a person's risk to develop GA. Diagnosis of GA is made by the appearance of skin lesions and lack of other physical findings or symptoms. GA may be confirmed by a biopsy and tests may be performed to rule out other associated diseases.

GA usually goes away without treatment within a few weeks to several years. However GA can sometimes last for decades, especially the generalized form. Steroids creams or injections and other therapies may be used to clear the rash more quickly, but are not successful in all cases, especially for those with the generalized form. Even after GA completely goes away, it may develop again.

Signs of granuloma annulare (GA) vary depending on the specific form:

• Localized GA presents with small, skin-colored or reddish firm bumps (erythematous papules) on the back of arms, wrists, ankles, hands, and feet. The bumps are usually, but not always, arranged in a circular or ring pattern. Involvement of the palms of the hands, face, scalp, and genitals is rare. Lesions of localized GA typically grow slowly, and in about 50% of the cases there is more than one lesion.
• Generalized GA may present as widespread bumps (papules), multiple ring shaped, raised patches (plaques), and/or large discolored, oddly shaped plaques. The color of the papules and plaques may be skin color, yellow, reddish pink, or violet. The sizes of the plaques may range from millimeters to several centimeters in diameter. The lesions of generalized GA can form anywhere on the body, but are most common on the trunk, arms, and legs. Generalized GA can affect the neck, face, scalp, soles of feet, and palms of hands.
• Subcutaneous GA presents with painless, round, firm lumps (nodules) that develop under the skin on the knees, ankles, feet, hands, scalp, eyelids, and/or buttocks. There can be one lump or a cluster of lumps. The lumps are usually less than 4 cm in size. The skin over the lumps may be skin colored, pink, or red, but otherwise normal in appearance. In some cases, the lumps of subcutaneous GA may grow quickly.
• Perforating GA presents with small bumps with crusted centers (umbilicated papules) that may leak fluid, itch, and be painful. The bumps may feel scaly and become filled with pus or ulcerate. This rare form usually affects the hands and fingers. However perforated GA may develop anywhere on the body, especially in scars. A person may have a few bumps or many bumps that join together to form raised patches of skin (plaques). This is the only type of GA that usually leaves scars when it heals.
• Patch GA presents with patch-like lesions that may be localized or generalized and are most commonly located in the legs or arms. The patches may be red, reddish brown, or violet.

Children tend to get the localized and subcutaneous types of granuloma annulare. The generalized and perforating types are more common in older adults.

In addition to the above forms, GA has been reported to occur in a linear pattern or as very painful papules or plaques.

In general, other than the perforating form and some very rare forms, GA does not cause symptoms such as pain or itching, and the skin will clear completely without scarring when it goes away.