Linear IgA disease: symptoms, diagnosis and treatment in the UK

Linear IgA disease is a long-term blistering condition of the skin. Under a microscope, a skin sample from an affected person shows IgA antibodies lined up along the thin layer where the outer skin (the epidermis) joins the layer beneath. The British Association of Dermatologists explains that this is how the condition gets its name, and that the antibodies are thought to damage structures in the skin so that blisters can form.

The condition is an immunobullous disorder, meaning that the body's own antibodies target the skin. The Primary Care Dermatology Society (PCDS) notes that the antibodies are directed against components of the basement membrane zone, the structure that anchors the epidermis to the deeper skin.

It affects both adults and children. In adults it is usually called linear IgA disease. In children the same pattern is known as chronic bullous disease of childhood. PCDS says presentation in children begins between about 6 months and 10 years of age, and in adults between 14 and 83 years, with a mean age of 52.

BAD describes the symptoms as ranging from mild itching to a severe burning sensation. The typical picture is an itchy rash with small blisters, often arranged in clusters or rings. The blisters can appear widely over the body and limbs or only in a few areas.

Some people notice the so-called string of pearls sign, in which blisters sit around the rim of red patches. BAD adds that blisters may heal to leave temporarily discoloured areas of skin, particularly in people with darker skin. Skin lesions tend to heal without leaving permanent scars.

• Itchy or burning rash with small blisters, often in clusters or rings.

• Blisters or ulcers in the mouth, eyes or genital region, which BAD says affect most adults with the condition.

• In children, a rash often in the genital region and on the face, especially around the mouth (BAD).

• Redness and a sore, gritty feeling in the eyes, which BAD says should prompt you to ask to see an eye specialist.

Often no cause can be found. BAD says infections and some medicines, most commonly the antibiotic vancomycin, may trigger the disease. PCDS lists other medicines reported in association with it, including penicillins, diclofenac and other anti-inflammatory painkillers, and says drug-induced disease resolves when the offending medicine is withdrawn.

Both sources mention occasional links with other conditions. BAD reports that linear IgA is more common in some people with other autoimmune diseases, such as ulcerative colitis, and with certain cancers. PCDS says it has rarely been associated with lymphoproliferative disorders and inflammatory bowel disease. These associations are uncommon, and most people with linear IgA disease have no such condition.

If you have started a new medicine shortly before blisters appeared, tell the doctor. Do not stop a prescribed medicine on your own, because the decision needs to weigh up what that medicine is treating.

BAD acknowledges that linear IgA can be difficult for doctors to diagnose. Confirmation requires a skin biopsy: small pieces of skin are removed after numbing with a local anaesthetic injection, and one or two stitches are usually placed afterwards. The sample is examined with direct immunofluorescence, a special test that can show the line of IgA under the epidermis.

PCDS describes the usual approach in more detail. Two biopsies are taken, one of an intact blister for ordinary microscopy and a second of the skin next to the blister for direct immunofluorescence, which has to be examined the same day or placed in a suitable transport medium. It adds that the immunofluorescence result can occasionally be falsely negative, so a further sample may be needed. PCDS also notes that blood tests for skin antibodies find IgA antibodies in roughly half of people.

Because the condition is so uncommon, PCDS says nearly all patients are referred to secondary care (hospital dermatology) for diagnosis and management.

The choice depends on how severe the disease is. According to BAD, mild disease can be treated with topical steroids alone, while most people do well with tablets such as dapsone. Other medicines that may be used include sulphonamides, steroids, ciclosporin, mycophenolate mofetil, intravenous immunoglobulins and colchicine, and antibiotics such as tetracyclines or erythromycin have also been used, particularly in children.

PCDS gives a stepwise outline for clinicians. Supportive measures include wound care and antiseptic washes or emollients to reduce the risk of secondary infection. Potent or super-potent topical steroids suit mild disease. For moderate to severe disease, which it says is the majority, erythromycin is tried first in children and dapsone is first-line in adults.

Dapsone needs monitoring. PCDS says a blood test for glucose-6-phosphate dehydrogenase (G6PD) deficiency is needed before starting, because deficiency raises the risk of dapsone-related haemolytic anaemia. Regular blood tests are required during treatment. People taking it are advised to stop and report immediately if they develop a skin rash, a high temperature, a sore throat, mouth ulcers, or unexplained bruising or bleeding.

BAD states that in the majority of people the disease eventually resolves after years, and that if a medicine caused it, stopping the drug usually clears it. PCDS points out that although the condition usually settles on its own, many people need treatment for long periods because lowering the dose often brings back blistering.

Skin lesions generally heal without scarring, but BAD warns that ulcers in the eyes, mouth or genital region can leave scars or cause lasting damage. That is why eye symptoms in particular should be reported early. PCDS adds that mucosal lesions respond less well to treatment than skin lesions.

Living with a long-term blistering condition can be tiring and sore. Gentle wound care, keeping blisters clean and attending monitoring appointments for blood tests are practical parts of day-to-day management.

In the UK, a GP who suspects a blistering disease would normally refer to NHS dermatology, where biopsy with immunofluorescence testing and specialist prescribing are available. Some people choose to see a consultant dermatologist privately for a faster appointment, but the same specialist tests and monitoring are involved, and ongoing prescribing of drugs like dapsone is usually shared with or overseen by a specialist team.