What is granuloma annulare?
Granuloma annulare (GA) is a common skin condition in which there are smooth discoloured plaques. They are usually thickened and ring-shaped or annular in shape. Granuloma annulare is more correctly known as necrobiotic papulosis. There are several clinical patterns.
Who gets granuloma annulare?
Granuloma annulare affects the skin of children, teenagers or young adults (or older adults, less commonly).
What is the cause of granuloma annulare?
Granuloma annulare is a delayed hypersensitivity reaction to some component of the dermis. Inflammation is mediated by tumour necrosis factor alpha (TNFα). The reason that this occurs is unknown.
Localised granuloma annulare is sometimes associated with autoimmune thyroiditis but it does not clear up with thyroid replacement. Extensive granuloma annulare is sometimes associated with diabetes mellitus, hyperlipidaemia, and rarely with lymphoma, HIV infection and solid tumours.
What are the clinical features of granuloma annulare?
Granuloma annulare can occur on any site of the body and is occasionally quite widespread. It only affects the skin. Granuloma annulare may cause no symptoms, but affected areas are often tender when knocked. The plaques tend to slowly change shape, size and position.
Localised granuloma annulare
The localised form is the most common type of granuloma annulare in children. One or more skin coloured bumps occur in rings in the skin over joints, particularly the knuckles. The centre of each ring is often a little depressed. Localised granuloma annulare usually affects the fingers or the backs of both hands, but is also common on top of the foot or ankle, and over one or both elbows.
Generalised granuloma annulare
Generalised granuloma annulare usually presents in adults, as widespread skin-coloured, pinkish or slightly mauve-coloured patches. The disseminated type is composed of small papules, usually arranged symmetrically in rings 10 cm or more in diameter. They are often found around the skin folds of the trunk (armpits, groin).
Subcutaneous granuloma annulare
Subcutaneous granuloma annulare most often occurs in children and presents as rubbery lumps. They appear on scalp margins, fingertips and shins. Subcutaneous granuloma annulare is also called pseudo-rheumatoid nodules because the subcutaneous lesions look rather like rheumatoid nodules. However, they arise in people that do not suffer from rheumatoid arthritis.
Perforating granuloma annulare
Perforating granuloma annulare describes plaques in which damaged collagen is eliminated through the epidermis. Perforating granuloma annulare is usually localised to the hands but plaques may occasionally arise on any body site, especially within scars. Dermatoscopy helps to confirm the presence of perforations in small papules arising within otherwise typical plaques of granuloma annulare. Perforating lesions are frequently itchy or tender.
Atypical granuloma annulare
Atypical granuloma annulare describes:
- Granuloma annulare in unusual sites, such as face, palms and ears
- Granuloma annulare with photosensitive distribution
- Unusually severe or symptomatic granuloma annulare
Interstitial granulomatous dermatitis
Interstitial granulomatous dermatitis is a pathological finding noted in some patients with extensive granuloma annulare or other disorders with similar clinical presentation.
How is granuloma annulare diagnosed?
Most often granuloma annulare is recognised clinically because of its characteristic appearance. But sometimes the diagnosis is not obvious, and other conditions may be considered. Skin biopsy usually shows necrobiotic degeneration of dermal collagen surrounded by an inflammatory reaction. It is not a true granuloma.
What treatment is available for granuloma annulare?
In most cases of granuloma annulare, no treatment is required because the patches disappear by themselves in a few months, leaving no trace. However, sometimes they persist for years. Treatment is not always successful.
Options to consider include:
- Topical corticosteroid ointment under occlusion
- Intralesional steroid injections
- Destruction by cryotherapy or laser ablation
- Imiquimod cream
- Topical calcineurin inhibitors (tacrolimus and pimecrolimus)
Systemic therapy may be considered in widespread granuloma annulare. The following treatments have been reported to help at least some cases of disseminated granuloma annulare. None of these can be relied upon to clear it, and there are some potential adverse effects.
- Systemic steroids
- Potassium iodide
- Allopurinol (note: allopurinol has also be cited as cause of disseminated granuloma annulare)
- Combination of antibiotics once monthly: rifampicin, oflaxacin, minocycline
- Photochemotherapy (PUVA)
- UVA1 phototherapy (not available in New Zealand)
- Photodynamic therapy
- Biologics particularly TNFα inhibitors such as adalimumab and infliximab
What is the outlook for granuloma annulare?
Localised granuloma annulare tends to clear up within a few months or years, although it may recur. Generalised and atypical variants are more persistent, sometimes lasting decades.