Granuloma annulare is a benign skin condition that causes raised, ring-shaped bumps or plaques, most often on the hands, feet, elbows, or knees. It is not contagious, not cancerous, and in most cases resolves on its own. While the appearance can be alarming, the condition is generally painless and harmless, though widespread forms can be itchy and persistent enough to warrant treatment.
What It Looks Like
The hallmark of granuloma annulare is a ring or arc of small, firm bumps that slowly expand outward. The bumps are typically skin-colored, reddish, or slightly purple, and the skin in the center of the ring often looks flat or slightly sunken. Unlike ringworm, which it’s frequently mistaken for, granuloma annulare doesn’t flake or scale, and it’s not caused by a fungus.
Most people develop one to a few rings, usually on the backs of the hands, tops of the feet, wrists, or elbows. The bumps tend to grow slowly over weeks to months, and rings can range from the size of a coin to several inches across. The localized form, which accounts for the majority of cases, is typically painless and causes no itching.
Types of Granuloma Annulare
The localized form is by far the most common. In a study of 407 patients, about 75% had localized disease, meaning just one or a handful of rings in a single area. This type affects both children and adults equally.
The generalized form makes up roughly 15% of cases and looks quite different. Instead of a few neat rings, it produces numerous papules and plaques scattered across the trunk, arms, and legs. This form is more common in adults and, unlike localized granuloma annulare, is often itchy. It’s also more stubborn and less likely to clear up quickly on its own.
Less common variants include a subcutaneous form, where firm nodules develop under the skin (most often in children), a perforating form where the bumps develop a central crust and drain a clear fluid, and a flat patch form that can resemble other skin conditions.
What Happens Under the Skin
Under a microscope, granuloma annulare shows a distinctive pattern: immune cells called histiocytes cluster together and surround pockets of damaged collagen. The collagen fibers in these areas become swollen and break down, a process called necrobiosis. The spaces left behind fill with a gel-like substance called mucin, which distinguishes granuloma annulare from similar-looking conditions.
The exact reason this happens is still not fully understood, but the immune system plays a central role. The body appears to mount an inflammatory response against its own collagen in the skin, recruiting both histiocytes and lymphocytes to the area. Research has identified abnormal activity in several immune signaling pathways in affected skin, pointing toward a process that looks more autoimmune than infectious.
Known Triggers and Risk Factors
For many people, granuloma annulare appears without any obvious cause. But documented triggers include skin trauma of various kinds: insect bites, tattoos, sun exposure, and even herpes zoster (shingles) outbreaks. Vaccination has been linked to granuloma annulare in rare cases, most often after the BCG vaccine but also after hepatitis B, influenza, tetanus, and COVID-19 vaccines.
Viral infections may also play a role. Granuloma annulare has been associated with Epstein-Barr virus, herpes viruses, and HIV. Some researchers have noted that many of the viruses linked to the condition are ones that establish long-term latency in the body, suggesting a connection between chronic viral presence and the immune response that drives the skin changes.
Links to Diabetes and Other Conditions
One of the most studied associations is with type 2 diabetes. A large population-based study found that 21.1% of people with granuloma annulare had diabetes, compared to 13.3% of matched controls. After adjusting for other factors, people with granuloma annulare were about 67% more likely to have diabetes. They were also more likely to develop diabetes in the future, with a 31% higher rate of new diabetes diagnoses during follow-up.
The same study found associations with high cholesterol and autoimmune conditions. Separately, clinical reports have linked granuloma annulare to autoimmune thyroid disease. In one review of 100 patients with generalized granuloma annulare, 13 had thyroid disease and 21 had diabetes. These links don’t mean granuloma annulare causes these conditions or vice versa, but the overlap is common enough that your doctor may check your blood sugar and thyroid function if you’re diagnosed.
How It’s Diagnosed
A dermatologist can often diagnose granuloma annulare just by looking at it. The ring-shaped pattern, the lack of scaling, and the typical locations are usually enough. When the appearance is ambiguous, or to rule out conditions like ringworm, sarcoidosis, or lichen planus, a small skin biopsy confirms the diagnosis. Under the microscope, the combination of palisading immune cells and mucin deposits is highly characteristic.
Treatment Options
Because localized granuloma annulare tends to resolve on its own, many people don’t need treatment at all. Rings commonly fade over months to a couple of years, though they can recur in the same spot or elsewhere.
When treatment is desired, either for cosmetic reasons or because the lesions are symptomatic, high-potency topical steroids are the standard first step. In a study of 61 patients with generalized disease, topical steroids kept things stable in about 47% of patients and produced partial clearing in another 19%. Full clearance occurred in about 10%. For individual stubborn lesions, steroid injections directly into the ring are highly effective, with one analysis reporting combined full and partial clearance in all treated patients.
For generalized granuloma annulare that doesn’t respond to topical treatment, phototherapy using UV light is a common next option. Beyond that, treatments become more specialized and less well-studied. Newer research into the immune pathways involved has opened the door to targeted therapies that block specific inflammatory signals, though these are still being evaluated for this particular condition.
What to Expect Over Time
Localized granuloma annulare has a generally favorable outlook. Most cases eventually clear, though the timeline is unpredictable. Some rings disappear in a few months, while others linger for years. Recurrence is common, with new rings appearing after old ones fade, sometimes in the same location.
Generalized granuloma annulare tends to be more persistent and harder to manage. It often follows a waxing-and-waning course over years, with periods of improvement followed by flare-ups. The condition leaves no scarring in most cases, though the perforating variant can occasionally leave small marks where lesions have drained. Granuloma annulare does not progress to skin cancer or cause damage to internal organs.