Linear IgA disease

Linear IgA disease is a rare blistering disorder. It is nearly identical to a similar condition that affects children, chronic bullous disease of childhood.

Chronic bullous disease of childhood usually presents before puberty with an abrupt onset of blistering in the genital region, later affecting hands, feet and face. In adults with linear IgA disease, the limbs are more often the first sites, although any area of the body may be affected later.

Clinical features

Clear round or oval blisters may arise from normal-looking or red skin. Red flat or elevated patches may arise, studded with small blisters (vesicles) or large ones (bullae), often target-shaped. The tendency for new blisters to arise in a ring around an old one is called the string of beads sign, and groups of small blisters may be described as a cluster of jewels. Crusts, scratch-marks, sores and ulcers may arise. The lesions can resemble other uncommon blistering skin diseases especially erythema multiforme, bullous pemphigoid and dermatitis herpetiformis.

The intensity of itching is variable. Blisters and ulceration on the lips and inside the mouth affect about 50%. Eye involvement may result in irritation, dryness, light sensitivity, blurred vision, corneal scarring and even blindness.

Linear IgA disease

	String of beads sign	Chronic bullous disease of childhood

Cause

Linear IgA disease is usually idiopathic i.e. it arises spontaneously. However, it sometimes follows infection and is rarely caused by drug allergy. Vancomycin is the most frequently associated drug, although diclofenac, captopril, cotrimoxazole, amiodarone, ciclosporin, glibencamide, lithium, penicillin, cefamandole, phenytoin, sodium hypochlorite, and somatostatin have been implicated in case reports. Drug-induced disease resolves with withdrawal of the offending agent. Linear IgA disease has also been rarely associated with lymphoma, haematological conditions, rheumatological conditions, ulcerative colitis and solid tumours.

Biopsy findings

Linear IgA disease is a subepidermal blistering disorder. This means that a skin biopsy reports blistering just under the epidermis as opposed to some blistering disorders that result in blistering within the epidermis eg pemphigus.

A special skin biopsy antibody test, direct immunofluorescence, reveals the immunoglobulin IgA along the basement membrane of the epidermis in a linear pattern. Sometimes these IgA antibodies can be detected by a blood test (indirect immunofluorescence). Research indicates the antibodies are directed against various basement membrane components (target antigens).

Linear deposition of IgA	No deposition of IgG
Direct immunofluorescence

Treatment

Most patients with Linear IgA disease improve or clear with Dapsone 50 to 100mg daily. Other medications that have been reported to help individual patients include:

• Corticosteroids (prednisone or prednisolone)
• Tetracycline antibiotics
• Erythromycin.
• Sulfapyridine
• Colchicine
• Mycophenolate mofetil
• Intravenous immunoglobulins

Although the condition may eventually be cured, many patients require long-term treatment as a reduction in dose of medication results in further blistering.