Dr Rosie Chellet, Medical Registrar, Christchurch Hospital, Christchurch, New Zealand. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, New Zealand. Copy edited by Gus Mitchell. April 2019.
The immune system is made up of the cells, molecules and structures that defend the body from infectious disease and monitor for tissue damage .
Immune responses can be divided into innate immunity and adaptive immunity.
Innate immunity describes generalised measures to ward off infection. These include:
Innate immune responses are often accompanied by inflammation .
Adaptive immunity describes slower immune responses, including the production of immune cells that produce specific antibodies to target and remove a particular microorganism .
Adaptive immunity results in the production of memory T lymphocytes and B lymphocytes that are able to specifically target a particular infection. These lymphocytes continue to circulate and quickly recognise and remove the virus or bacteria when it is next encountered .
Autoimmunity is an immune response against the self and usually involves T and B lymphocytes. The particular targeted protein or structure is called the self-antigen .
Autoimmunity may result in autoimmune disease with tissue damage or impaired physiological function. Autoimmune responses may also occur without causing disease .
Antibodies that react against self-antigens are called autoantibodies. In some autoimmune diseases, autoantibodies are the direct cause of tissue damage. In others, autoantibodies may be present without causing injury .
Examples of autoimmune diseases include:
Autoimmune blistering skin diseases include:
Autoimmunity and deregulation of the immune system also contribute to many skin diseases, such as:
Autoimmune diseases affect around 5% of the population .
Autoimmune disease occurs when the responses that normally prevent autoimmunity fail . There are several protective mechanisms.
The exact cause of a particular autoimmune disease is often not fully understood. Risk factors for many autoimmune diseases include genetic factors, infections, hormones, and drugs.
Well-designed trials have concluded that there is no evidence that vaccines cause autoimmune disease .
The autoimmune cause of this class of blistering diseases is confirmed by positive direct immunofluorescence microscopy revealing the deposition of antibodies in the skin.
Pemphigus is a group of rare blistering disorders caused by circulating autoantibodies that bind to adhesion molecules in the skin, which disrupts the way keratinocytes stick together, causing intraepidermal blisters . The main types of pemphigus are pemphigus vulgaris, pemphigus foliaceus, and paraneoplastic pemphigus .
The pemphigoid group of diseases includes bullous pemphigoid, mucous membrane pemphigoid, and pemphigoid gestationis. Pemphigoid blisters are subepidermal and are caused by autoantibodies that bind in the area of the dermal-epidermal junction .
Dermatitis herpetiformis is an itchy blistering skin disease that typically affects elbows, knees and buttocks. It is associated with coeliac disease, and the symptoms heal with a gluten-free diet . Blisters and deposition of IgA are subepidermal and a neutrophilic infiltrate is characteristic. The antibodies target epidermal transglutaminase .
Linear IgA bullous dermatosis is a very rare autoimmune blistering disorder that can be acquired or drug-induced (eg, by vancomycin). The blisters are sometimes arranged in rings, known as the ‘pearl necklace’ sign . There is subepidermal deposition of IgA antibodies targeting a portion of the BP180 antigen, type VII collagen, or other basement membrane proteins.
Epidermolysis bullosa acquisita is also very rare. In the classical form, blisters and erosions form at areas of minor trauma . The autoantibodies are directed against type VII collagen in anchoring fibrils in the basement membrane zone of the skin and mucosa.
A biopsy is usually needed for a definitive diagnosis of an autoimmune skin disease, although a characteristic appearance may be suggestive of a particular condition .
Blood tests may include:
Blistering skin rashes associated with systemic illness may present with fever and ‘flu-like' symptoms . These disorders can include:
Other generalised blistering disorders that present with autoimmune skin disease symptoms include:
Blistering of mucous membranes is also a common symptom in these conditions:
The treatment of autoimmune skin diseases depends on the specific condition.
See the DermNet NZ bookstore.
© 2019 DermNet New Zealand Trust.
DermNet NZ does not provide an online consultation service. If you have any concerns with your skin or its treatment, see a dermatologist for advice.