Granuloma annulare

Signs of granuloma annulare (GA) vary depending on the specific form:^{[1][2][3][4][5]}

• 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 and may cause itching.^[3] 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.^[1][2]

In addition to the above forms, GA has been reported to occur in a linear pattern or as very painful papules or plaques.^[3]

The cause of granuloma annulare (GA) is unknown but many researchers have proposed it may involve an immune and/or inflammatory response.^[3][4][6]  While most cases occur in people who are otherwise healthy, there are a number of triggers and associated diseases. It has been reported to follow insect bites, sun exposure, tuberculin skin tests, tattoos, other injuries to the skin, certain medications (allopurinol, diclofenac, quinidine, calcitonin, amlodipine, ACE inhibitors, daclizumab, and calcium channel blockers), and viral infections (including Epstein-Barr, hepatitis C, herpes zoster, and HIV). GA has been associated with the development of other medical conditions including  autoimmune thyroiditis, diabetes, dyslipidemia, and cancer.^[1][3][4][5] Chronic stress may be another trigger.^[1] However, researchers do not understand why GA only develops in a few people who are exposed to any of these triggers. Although a genetic predisposition to develop GA has been proposed, no specific genetic change (variant) has been found.^[1][3][5]

Since there are many different triggers and possible associated diseases, as well as different forms of GA, some researchers suggest that there is no single cause of GA, but rather multiple pathways that when triggered can lead to the development of this skin disorder.^[6] 

If granuloma annulare (GA) does not cause bothersome symptoms like itching, then it usually does not need to be treated.^[3][7] If GA does cause symptoms, it can be difficult to find the best treatment, because treatment options for GA have not been studied in large clinical trials. Information about treatment options is available only through published reports from individual cases, a small number of cases, or small uncontrolled studies.^[3][4]

The localized form of GA may be treated with topical steroid creams, topical tacrolimus or pimecrolimus,  freezing the lesions (cryotherapy), or laser therapy. Injecting triamcinolone acetonide, a type of steroid, into lesions has also been successful in some cases. In general, steroid creams are usually tried first.^[3][4][7]

The generalized form of granuloma annulare can be more difficult to treat and many treatment options have been tried. Again, the first treatment is usually topical steroid cream or steroid injections into the lesions. These treatments work best before the lesions are very widespread. Predinsone taken orally (systemic steroid treatment) may also be effective early in the treatment of generalized GA, but the lesions may return when the steroid treatment is stopped. Light therapy, also called phototherapy, is the next main treatment option and involves exposing the skin to ultraviolet light. Light therapy options may include UVA1 phototherapy, PUVA photochemotherapy, or photodynamic therapy.^[3][4]

Other medications that may be given for generalized granuloma annulare include hydroxychloroquine, isotretinoin, or dapsone. Combinations of certain antibiotics (rifampin, ofloxacin, and minocycline) have been shown to be successful in some cases. For people with very severe disease, treatment options may include cyclosporine, infliximab, or adalimumab.^[3][4][7] In Europe where fumeric ester acids (FEA) have been approved for the treatment of severe psoriasis, FEA has been reported to be effective in treating some cases of generalized GA.^[4]

Many of these treatments have shown results in only a few patients and can have side effects. The risks and benefits of each treatment option should be discussed with your doctor.^[3][4]

For most people, granuloma annulare (GA) goes away within a few years. It tends to last longer if it has spread to more parts of the body (generalized form) than if it is found in just one location (localized form). The generalized form may follow a pattern of spontaneously healing only to develop months or years later. About 25% of cases of generalized GA last for more than five years and for some it may last longer than 10 years.^[3]