Linear IgA bullous disease
What is linear IgA bullous disease?
Linear IgA bullous disease is an autoimmune skin disorder in which blisters form in the skin and mucous membranes. Its name comes from the characteristic findings on direct immunofluorescence of a skin biopsy, in which a line of IgA antibodies can be found just below the epidermis. It is also called linear IgA disease, and in children, chronic bullous disease of childhood.
Who gets linear IgA bullous disease?
Linear IgA bullous disease affects adults of all ages, but is most common in old age. It is very rare.
Childhood linear IgA bullous dermatosis is also rare. It has been suggested that it may be more common in children in developing countries. It is most frequent in preschool children.
What are the clinical features of linear IgA bullous disease?
Linear IgA bullous disease is characterised by blisters on the skin and mucous membranes.They tend to start on the limbs, but any area of the body may be affected. Blisters and ulcers on the lips and inside the mouth affect about 50% of people with linear IgA disease.
In children, linear IgA bullous disease usually presents before puberty with an abrupt onset of blistering in the genital region, later affecting hands, feet, face and limbs.
Round or oval blisters filled with clear fluid may arise from normal-looking skin or from red flat or elevated patches. The blisters may be small (vesicles) or large (bullae). Typically, the blisters are arranged in rings (annular lesions) and they may form a target shape. 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. Secondary lesions include crusts, scratch-marks, sores and ulcers.
Eye involvement may result in irritation, dryness, light sensitivity, blurred vision, corneal scarring and even blindness.
The intensity of itching is variable in linear IgA disease.
What is the cause of linear IgA bullous disease?
The cause of linear IgA bullous disease is not fully understood. It is classified as an autoimmune skin disease. Blistering occurs because of the development of a split between the epidermis and the dermis, where IgA autoantibodies react to components of the hemidesmosome and basement membrane (BP180, BP230 and LAD285).
Linear IgA bullous disease usually arises spontaneously but it can be triggered by infection.
Underlying disease associations
Linear IgA bullous dermatosis has been reported in patients with inflammatory bowel disease. It is thought that autoantigens are exposed to the immune system in the diseased colon, and the same autoantigens are then targeted in the skin. Surgery to remove bowel can lead to clearance of the blistering skin disease.
Linear IgA bullous dermatosis has also been rarely associated lymphoma, haematological conditions, rheumatological conditions, and solid tumours.
Drug-induced linear IgA bullous dermatosis
Linear IgA bullous dermatosis has been reported to have been caused by drugs. The most frequently associated drugs are:
- Sodium hypochlorite (bleach)
Drug-induced disease resolves with withdrawal of the offending agent.
Linear IgA bullous disease presenting as toxic epidermal necrolysis
Toxic epidermal necrolysis (TEN) is a severe cutaneous adverse reaction to a drug that presents with widespread painful loss of skin and blistering. A few cases have been described in which direct immunofluorescence has revealed characteristic linear deposits of IgA.
*The patient illustrated above developed a TEN-like eruption when prescribed dapsone, which is normally beneficial in linear IgA disease.
What are the biopsy findings?
Linear IgA bullous dermatosis is a subepidermal blistering disorder. This means that a skin biopsy reports blistering just under the epidermis. It is associated with inflammation in which eosinophils and neutrophils are prominent.
A special skin biopsy antibody stain, direct immunofluorescence, reveals the immunoglobulin IgA along the basement membrane of the epidermis in a linear pattern. Sometimes these IgA antibodies can also be detected by a blood test (indirect immunofluorescence).
It is sometimes difficult to distinguish different forms of immunobullous diseases clinically and histologically, and antibody findings may overlap.
Direct immunofluorescence in linear IgA bullous dermatosis
What is the treatment for linear IgA bullous dermatosis?
Most patients with Linear IgA bullous dermatosis improve or clear with dapsone 50–100 mg daily. Other medications that have been reported to help individual patients include:
- Corticosteroids (prednisone or prednisolone)
- Tetracycline antibiotics (not suitable in children under 8 years of age)
- Mycophenolate mofetil
- Intravenous immunoglobulins
Although linear IgA bullous dermatosis may eventually clear up, many patients require long-term treatment, as a reduction in dose of medication results in further blistering.