Granuloma annulare is a benign, inflammatory skin condition that is characterized by the formation of papules (small, solid bumps) that arrange themselves into a ring or “annular” shape. The name itself describes what a pathologist sees under a microscope: a granuloma is a specific type of inflammation where immune cells cluster together, and annulare refers to the ring-like shape of the lesions.

To understand what is happening, it is helpful to use an analogy.

• Think of the deeper layer of your skin (the dermis) as a quiet field.
• In granuloma annulare, for reasons that are not entirely clear, the body’s “cleanup crew” immune cells (a type of white blood cell called a macrophage) receive a faulty signal.
• They swarm into a small area of the field and, instead of cleaning up a problem, they begin to wall off a small section of normal tissue components, like fragments of collagen or elastic fibers.
• They surround this area and form a dense, circular wall or palisade like a group of people linking arms in a tight circle.
• This microscopic, ring-shaped collection of inflammatory cells is a granuloma. It is this structure deep in the skin that pushes up from below to create the visible, ring-shaped bump that you see on the surface.

There are several different clinical types of granuloma annulare:

• Localized Granuloma Annulare: This is the most common form, characterized by one or a few rings, typically on the hands or feet.
• Generalized Granuloma Annulare: In this form, which is more common in adults, there can be dozens or even hundreds of rings or papules, often appearing on the trunk, arms, and legs.
• Subcutaneous Granuloma Annulare: This type typically affects children and presents as firm, deep lumps under the skin, often on the scalp, hands, and shins.
• Perforating Granuloma Annulare: A rare form where the center of the lesion breaks down and may ooze a small amount of fluid.

In my experience, patients often come in worried their rash is contagious or related to ringworm. But granuloma annulare is actually harmless and non-infectious.

The exact cause of granuloma annulare is unknown. It is not an infection. It is believed to be a type of delayed-type hypersensitivity reaction, meaning it is a specific reaction pattern of the body’s immune system. It is thought that the body’s T-lymphocytes, a key type of immune cell, are the primary drivers of the inflammatory process that leads to the formation of the granulomas. What triggers this specific reaction in the first place is often unclear.

In my experience, it often develops without any clear cause. Patients are often surprised to learn it may just appear spontaneously and linger for months or years.

A person develops granuloma annulare spontaneously. It is not contagious, and you cannot “get it” from or give it to another person. While it is not considered a directly inherited disease, there may be a genetic predisposition that makes some people more likely to develop this particular skin reaction.

While the cause is unknown, in some individuals, the onset of the lesions has been associated with certain potential triggers. These include:

• Minor skin injuries or trauma.
• Insect bites.
• Certain viral infections.
• Tuberculin skin tests.
• Sun exposure.

Associated Medical Conditions

In most cases, granuloma annulare, especially the localized form, occurs in otherwise perfectly healthy individuals. However, there is a recognized association between the generalized form of granuloma annulare and certain systemic diseases.

• Diabetes Mellitus: People with generalized granuloma annulare may have a higher incidence of diabetes.
• Thyroid Disease: Both underactive (hypothyroidism) and overactive (hyperthyroidism) thyroid conditions have been linked to the condition.
• For this reason, a person diagnosed with widespread, generalized granuloma annulare will often have blood tests to screen for these conditions.

Clinically, the exact cause is unknown, but it’s thought to be an immune-mediated reaction in the skin possibly triggered by minor trauma, infections, or systemic conditions.

The primary sign of granuloma annulare is the appearance of the skin rash itself.

• Appearance: The condition typically begins with the appearance of small, firm, skin-colored, reddish, or purplish bumps (papules).
• Ring Shape: These small bumps slowly expand outward and join together over a period of weeks to months, forming a distinctive ring or annular shape. The border of the ring is raised and composed of small bumps, while the skin in the center is often slightly depressed and may appear normal or slightly pale.
• Location: The rash most commonly appears on the tops of the hands and feet, and on the ankles and wrists. It is often symmetrical, appearing on both sides of the body. In the generalized form, the rings can appear on the trunk, arms, and legs.
• Symptoms: In the vast majority of cases, the lesions of granuloma annulare are completely asymptomatic.
  • They do not typically cause pain.
  • Some individuals may experience mild itching, but severe itching is uncommon.
  • The primary “symptom” is the cosmetic appearance of the rash, which can be a source of concern or self-consciousness for the patient.

Clinically, I distinguish it from other rashes by its firm, annular (circular) shape and lack of scaling or significant discomfort.

A diagnosis of granuloma annulare is typically made by a dermatologist based on a clinical examination.

• Clinical Diagnosis: The diagnosis is often clear based on the characteristic clinical appearance of the smooth, non-scaly, ring-shaped plaques in a classic location like the hands or feet.
• Key Distinction from Ringworm: The most common condition that granuloma annulare is confused with by patients is tinea corporis, or ringworm. A dermatologist can easily tell them apart.
  • Granuloma Annulare: The ring is smooth, deep, and not scaly.
  • Ringworm: The ring has a raised, red, and very scaly border, and the center often has fine scale. It is usually very itchy.
  • A doctor can perform a simple KOH test, scraping the scale from a ringworm lesion to see the fungus under a microscope, which will be negative in granuloma annulare.
• Skin Biopsy: If the diagnosis is not perfectly clear, a skin biopsy is the gold standard for confirmation. A small sample of skin is taken from the raised border of a lesion. A pathologist will examine the tissue and see the characteristic “palisading granuloma” in the dermis, with immune cells arranged in a circle around a central area of altered collagen. This finding is definitive for granuloma annulare and also rules out other more serious conditions.
• Blood Tests: As mentioned, if a patient has the widespread, generalized form of the disease, a doctor will likely order blood tests to screen for diabetes and thyroid disease.

In my experience, patients sometimes undergo unnecessary antifungal treatments before the correct diagnosis is made, as it can resemble tinea (ringworm).

The most important aspect of treatment is reassurance. Because granuloma annulare is a benign and self-limiting condition in most cases, often the best treatment is no treatment at all.

Natural Course

It is crucial for patients to know that localized granuloma annulare has a high rate of spontaneous resolution. In about 50-75% of cases, the lesions will disappear on their own, without any treatment, within two years.

When is Treatment Considered?

Treatment is typically reserved for individuals who are significantly bothered by the cosmetic appearance of the lesions, if the rash is very widespread, or in the rare cases where it is causing itching or discomfort.

The treatment options follow a stepwise approach:

1. Topical Treatments

These are the first-line medical therapies and are applied directly to the skin.

• Topical Corticosteroids: A high-potency prescription steroid cream or ointment, applied to the lesions, can help to reduce the inflammation and flatten the bumps.
• Intralesional Steroid Injections: This is often one of the most effective treatments for localized granuloma annulare. A dermatologist will inject a small amount of a corticosteroid directly into the raised border of the ring. This can often lead to a rapid resolution of the lesion.
• Topical Calcineurin Inhibitors: These are non-steroid anti-inflammatory creams, like tacrolimus or pimecrolimus, which can be an alternative to steroids, especially for use on the face.

2. Phototherapy

For patients with widespread, generalized granuloma annulare, phototherapy is often an effective treatment option. This involves controlled exposure to specific wavelengths of ultraviolet (UV) light in a dermatologist’s office several times a week.

3. Systemic Medications

Oral medications are rarely used and are reserved for very severe, widespread, or disfiguring cases that have not responded to other treatments. A variety of systemic drugs have been tried with mixed success, including isotretinoin, hydroxychloroquine, and other immunosuppressants.

Clinically, I reserve systemic treatments like light therapy or oral medications for generalized or persistent cases that affect quality of life.

Granuloma annulare is a common and benign inflammatory skin condition that creates distinctive, ring-shaped rashes, most often on the hands and feet. While its appearance can be a source of cosmetic concern and can cause anxiety about more serious conditions, it is crucial to be reassured that it is a medically harmless issue. It is not contagious and does not represent an internal disease for most people. The key to management is a proper diagnosis from a dermatologist, which provides peace of mind and differentiates it from other rashes like ringworm. Clinically, I focus on symptom management and educating patients about the waxing and waning nature of granuloma annulare to set realistic expectations.

The American Academy of Dermatology (AAD). (n.d.). Granuloma Annulare: Overview. Retrieved from https://www.aad.org/public/diseases/a-z/granuloma-annulare-overview

The Mayo Clinic. (2022). Granuloma annulare. Retrieved from https://www.mayoclinic.org/diseases-conditions/granuloma-annulare/symptoms-causes/syc-20351329

DermNet NZ. (n.d.). Granuloma annulare. Retrieved from https://dermnetnz.org/topics/granuloma-annulare