Granuloma annulare (GA) is a benign granulomatous inflammatory disorder of the dermis or subcutis. Its cause is unknown. Small dermal papules may present in isolation or coalesce to form smooth annular plaques, often on extremities. Lesions are typically asymptomatic or only mildly pruritic, but the appearance may cause patients distress. The disease is more common in women (female-to-male ratio of 2:1), and two-thirds of patients are aged younger than 30. The disease usually resolves spontaneously with no adverse sequelae, although some cases prove persistent or recurrent.

Some reports in the literature have suggested that GA is associated with certain triggers or systemic diseases, most commonly diabetes mellitus; other diseases that may be associated include thyroid disease, dyslipidemia, malignancy, and infections.

There are 3 principal variants of GA: localized (75% of cases), generalized (or disseminated), and subcutaneous (also known as pseudo-rheumatoid nodules). Patch GA is a variant of localized GA in which the plaques are extremely thin and barely palpable. A fourth type – perforating GA – refers to rare lesions that demonstrate histologic evidence of transepidermal extrusion of degraded collagen. Actinic granuloma presents with similar lesions and is thought by some to represent GA occurring in sun-damaged skin. Palmoplantar GA is a rare variant favoring the palms.