Granuloma Annulare

Granuloma annulare (GA) is a common, sometimes chronic skin condition characterised by reddish bumps on the skin arranged in a circle or ring. It can occur at any age, but two-thirds of patients are under 30, and it is most often seen in children and young adults. Females are twice as likely to develop GA as males.

Signs and Symptoms

Granuloma annulare is typically asymptomatic aside from the visible rash. However, the rash may sometimes burn or itch. Patients usually notice a ring of small, firm bumps (papules) on the backs of the forearms, hands, or feet, often centred on joints or knuckles. These papules are caused by the clustering of T cells below the skin and can vary in size from small, pimple-like bumps to larger lesions. Occasionally, multiple rings may join into one. Rarely, GA may appear as a firm nodule under the skin of the arms or legs. The condition can persist for many years without treatment, with outbreaks continuing to develop at the edges of ageing rings.

Causes

Granuloma annulare is generally seen in otherwise healthy individuals. However, it can be associated with diabetes, thyroid disease, and autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, Lyme disease, and Addison's disease. Despite these associations, no conclusive connection has been established.

Pathology

Microscopically, granuloma annulare consists of dermal epithelioid histiocytes around a central zone of mucin, forming a palisaded granuloma.

Pathogenesis

Granuloma annulare is considered an idiopathic condition, although several potential catalysts have been proposed, including skin trauma, UV exposure, vaccinations, tuberculin skin testing, and infections from Borrelia and viruses.

The mechanisms at a molecular level are varied. One hypothesis by Dahl et al. (1977) suggests blood vessel involvement, with immunoglobin M (IgM), complement, and fibrinogen found in the blood vessels of GA areas, indicating a possible immune-mediated type 3 reaction or chronic immune vasculitis. Another hypothesis by Umbert et al. (1976) proposes cell-mediated immunity, with lymphokines like macrophage-inhibiting factor (MIF) leading to sequestration of macrophages and histiocytes in the dermis, resulting in connective tissue damage.

Diagnosis

Granuloma annulare can be divided into five types:

• Localised granuloma annulare
• Generalised granuloma annulare
• Patch-type granuloma annulare
• Subcutaneous granuloma annulare
• Perforating granuloma annulare

Treatment

Given that granuloma annulare is usually asymptomatic and self-limiting with a course of about two years, initial treatment typically involves topical steroids or calcineurin inhibitors. If topical treatments are ineffective, intradermal steroid injections or phototherapy may be used. Systemic corticosteroids may be considered if local treatments fail. Treatment success varies, with many patients experiencing only brief relief. Most lesions in pre-pubertal patients resolve without treatment within two years, while older patients (50+) may have rings for upwards of 20 years. It is not uncommon for new rings to appear years later.

History

The disease was first described in 1895 by Thomas Colcott Fox as a "ringed eruption of the fingers" and was named granuloma annulare by Henry Radcliffe Crocker in 1902.

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Self-assessment MCQs (single best answer)

Which age group is most commonly affected by Granuloma Annulare (GA)?

Granuloma Annulare is more common in which gender?

What is a typical symptom of Granuloma Annulare?

Where on the body are Granuloma Annulare lesions most commonly found?

Which of the following is NOT associated with Granuloma Annulare?

Microscopically, what is a characteristic feature of Granuloma Annulare?

What is one proposed trigger for Granuloma Annulare?

Which type of treatment is typically first used for Granuloma Annulare?

How long do Granuloma Annulare lesions typically last without treatment?

Who first named the condition "Granuloma Annulare"?