Granuloma Annulare

This is a benign inflammatory condition of unknown aetiology with dermal papules and annular plaques. Histology reveals foci of degenerative collagen with palisaded granulomatous inflammation. It may be associated with diabetes but association with systemic disease is rare.¹

5 variants of the condition are recognised:

1. Localised
2. Generalised
3. Subcutaneous
4. Perforating
5. Arcuate dermal erythema (some regard it as a separate entity)

It is an uncommon condition and figures on incidence are not available. Localised is the commonest type. Generalised represents about 10 to 15% of cases. Perforating is about 5%.

Women are affected twice as often as men. The localised variety is usually found under 30 years old. The generalised type has peaks at under 10 and 30 to 60 years. Subcutaneous affects children aged 2 to 10 and the perforating type is also a disease of children.

Both localised and generalised are usually asymptomatic lesions that may improve in winter and deteriorate in summer. The subcutaneous type is often a large subcutaneous mass. They may be stable for months and then enlarge over weeks.

Localised lesions are usually groups of papules, about 1 to 2mm in diameter with possible erythema. They tend to form an arc or a ring 1 to 5cm in diameter. The centre of lesions may be slightly depressed and hyperpigmented. They are usually on the dorsal surfaces of hands, feet and fingers and the extensor surface of arms and legs.

Generalised has a similar appearance to the lesions but they are more numerous and more diffuse. They may coalesce into annular plaques 3 to 6cm in diameter and these can expand over weeks or months. They tend to be on limbs or trunk.
Subcutaneous lesions are firm, skin-coloured or pink, not tender and the overlying skin looks normal. They are usually solitary lesions but can occur in clusters. The lower limb, especially the pretibial surface is the commonest area. Lesions are mobile, except on the scalp.

Perforating lesions are papules 1 to 4mm in diameter with possibly some degree of erythema. They may be solitary or number in hundreds but often coalesce to form annular plaques. They tend to be larger and more ulcerated in middle-aged or elderly people and the lesions may leave hyperpigmented or hypopigmented scars. They tend to be on the extensor surface or lower arms or legs or dorsal surface of hands.

Arcuate dermal erythema is the rarest form. It produces infiltrated erythematous patches that may form large, hyperpigmented rings with central clearing. Papules are less pronounced. Lesions typically appear on the trunk and may spread centrifugally over weeks to months.

Diagnosis is essentially clinical and laboratory tests are not helpful unless another diagnosis is suspected. If in doubt, biopsy may be helpful.

Lichen planus, sarcoidosis, rheumatoid nodules

The local type tends to be indolent but the generalised type may produce cosmetic embarrassment. A number of treatments are effective.

• Intralesional steroid injection is almost always effective for local disease but less effective, less practical and need more steroid in generalised disease..
• Potent steroid creams may be enhanced by using under occlusion.
• Cryotherapy works but may cause hypo or hyperpigmentation. Some regard it as the treatment of choice.²
• Generalised disease is not so amenable to the steroid treatment and is also less likely to resolve spontaneously. Systemic treatments have been disappointing. There are many options, none of which are satisfactory. They include PUVA³, oral steroids, dapsone, chlorambucil and cyclosporin. Trials have usually been small. The tumour necrosis factor inhibitor infliximab may be useful in recalcitrant cases.⁴
• With subcutaneous lesions in children the best management is reassurance.⁵
• Treatment of perforating lesions is disappointing.⁶

In untreated localised disease the lesions may last weeks or decades. Half will disappear inside 2 years but in 40% they will recur.
The prognosis for generalised disease is much worse with a chronic course, poor response to treatment, low chance of spontaneous remission and if it does occur, high risk of recurrence.
Subcutaneous lesion often resolve spontaneously but may recur elsewhere.