Granuloma annulare

Signs and symptoms

Aside from the visible rash, granuloma annulare is usually asymptomatic, though it may occasionally burn or itch. The condition typically presents as a ring of small, firm bumps over the backs of the forearms, hands, or feet, often centered on joints or knuckles. It can occur anywhere on the body, including the neck, back, ankles, and wrists.

Bumps start as very small, pimple-like lesions that spread over time to larger sizes, and multiple rings may join into one. Rarely, it appears as a firm nodule under the skin of the arms or legs. Without therapy, outbreaks can persist for many years, with new lesions developing at the edges of aging rings.

Pathology

Microscopically, granuloma annulare consists of dermal epithelioid histiocytes around a central zone of mucin, forming a palisaded granuloma. The condition is idiopathic, though proposed catalysts include skin trauma, UV exposure, vaccinations, tuberculin skin testing, and Borrelia and viral infections. Proposed molecular mechanisms vary. One study found immunoglobulin M, complement, and fibrinogen in blood vessels of affected areas, suggesting a possible immune-mediated type 3 reaction or chronic immune vasculitis.

Another study proposed cell-mediated immunity, suggesting that lymphokines such as macrophage-inhibiting factor lead to sequestration of macrophages and histiocytes in the dermis, with subsequent lysosomal enzyme release causing connective tissue damage. Later data supported the view that activation of macrophages and fibroblasts is involved, and that fibrin and rare IgM and C3 deposition around vessels likely reflect a delayed-type hypersensitivity rather than an immune-complex mediated disease.

Treatment

Because granuloma annulare is usually asymptomatic and self-limiting over about two years, initial treatment involves topical steroids or calcineurin inhibitors. If unimproved, intradermal steroid injections or phototherapy may be used, and systemic corticosteroids are considered if local treatment fails. Treatment success varies widely, with most patients experiencing only brief improvement. Lesions often disappear without treatment in pre-pubertal patients within two years, while older patients may have rings for up to 20 years, and new rings years later are not uncommon.

Did You Know?

• Granuloma annulare is usually seen in otherwise healthy people, but may occasionally be associated with diabetes or thyroid disease.
• It has also been linked to autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, Lyme disease, and Addison's disease.
• No conclusive connection has been made between patients with these conditions.