Granuloma annulare (GA) is a common condition of unknown cause which affects the skin of children, teenagers or young adults (or any age group, less commonly).
Granuloma annulare can occur on any site of the body and is occasionally quite widespread. It only affects the skin and is considered harmless. Granuloma annulare may cause no symptoms, but affected areas are often tender when knocked.
Often granuloma annulare will disappear after a few weeks or months without leaving a scar, but it may recur at the same site or somewhere else at a later date.
What does it look like?
There are several subtypes:
Localised granuloma annulare
The localised form is the most common type of granuloma annulare in children. Skin coloured bumps occur in rings often over joints, particularly the knuckles. The centre of each ring is often a little depressed. It 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. It tends to clear up within a few months or years, although it may recur. It is sometimes associated with autoimmune thyroiditis but granuloma annulare does not clear up with thyroid replacement.
Generalised granuloma annulare
Generalised granuloma annulare usually presents in adults, as widespread skin coloured, pinkish or slightly mauve-coloured groups of patches, or in the dessiminated type, small papules, usually arranged symmetrically in rings 10cm or more in diameter and often around the skin folds of the trunk (armpits, groin). Extensive granuloma annulare is sometimes associated with diabetes mellitus, hyperlipidaemia, and rarely with lymphoma, HIV infection and solid tumours.
Deep or subcutaneous granuloma annulare (pseudo-rheumatoid nodules)
Subcutaneous granuloma annulare is seen most often in children. It favours scalp margins, finger tips and shins. Nodules under the skin have a rubbery feel. They look rather like rheumatoid nodules but arise in people that do not suffer from rheumatoid arthritis.
Perforating granuloma annulare
Perforating granuloma annulare is uncommon, and is usually localised to the hands although it may be generalised and sometimes appears within scars. Damaged collagen is eliminated through the epidermis. The lesions are frequently itchy or tender.
Atypical granuloma annulare
Atypical granuloma annulare is when it arises in unusual sites, such as face, palms and ears, has a photosenstive distribution, or is unusually severe or symptomatic.
What is the cause of granuloma annulare?
Granuloma annulare is a delayed hypersensitivity reaction to some component of the dermis and inflammation is mediated by tumour necrosis factor alpha (TNFα). The reason this occurs is unknown.
How is granuloma annulare diagnosed?
Most often granuloma annulare is recognised because of its characteristic apppearance. But sometimes the diagnosis is not obvious, and other conditions may be considered. In such cases, a small biopsy (when a tiny piece of skin is removed under local anaesthetic) will help to establish the cause of the rash. The biopsy shows characteristic necrobiotic degeneration of dermal collagen surrounded by an inflammatory reaction.
What treatment is available for granuloma annulare?
In most cases no treatment is required because the patches disappear by themselves in a few months leaving no trace. However, sometimes they persist for years. Sometimes it is helpful to apply a strong steroid preparation to the skin or intralesional steroid injections can be used. Small plaques can be frozen (cryotherapy) or removed by laser ablation. Topical imiquimod and topical calcineurin inhibitors (tacrolimus and pimecrolimus) have been reported to help individual cases.
In very widespread cases, other treatments may be tried. The following agents 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
- Biological response mediators
Even if the treatment proves successful the granuloma annulare tends to return when it is discontinued.
On DermNet NZ:
- Skin signs of systemic disease
- Actinic granuloma
- Granuloma annulare pathology
- Interstitial granulomatous dermatitis
- Granuloma Annulare – Medscape Reference
- Granuloma annulare – British Association of Dermatologists
- Patient information: Granuloma annulare (The Basics) – UpToDate (for subscribers)
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