What is IgA?IgA is the most abundant antibody produced by the body, and is present both in the bloodstream as well as in a secreted form on the surface of mucus membranes. The most important role of IgA is to protect against infection from the numerous bacteria that are present on the mucus membranes. IgA acts to coat the surface of bacteria, which are then destroyed by a variety of immune mechanisms.
What is IgA Deficiency?IgA deficiency is defined as the complete absence, or extremely low values, of IgA as measured in the blood, in the setting of other antibody levels (IgG and IgM) being normal. Slightly low IgA values are not consistent with IgA deficiency.
While IgA deficiency is classified as a form of immunodeficiency, 85-90% of people with IgA deficiency have no symptoms related to their condition. Most people are diagnosed as a result of donating blood, in which approximately 1 in every 300 people are found to have IgA deficiency. IgA deficiency is caused by developmental abnormalities of certain white blood cells in the body (B-cells and/or T-cells), which is often due to genetic abnormalities that run in families.
What are the Symptoms of IgA Deficiency?Some, but not all, people with IgA deficiency are at an increased risk for infections that involve the mucus membranes, such as the sinuses (sinusitis), middle ears (otitis media), lungs (pneumonia), and gastrointestinal tract (Giardiasis). It is not understood why most people with IgA deficiency have no increase in infections whatsoever, and why some have many complications from this antibody deficiency.
IgA deficiency is also associated with other gastrointestinal diseases, including lactose intolerance, celiac disease and ulcerative colitis. Celiac disease is most commonly diagnosed by the presence of IgA antibodies against certain proteins in the gastrointestinal tract, which, of course, would not found in a person with both celiac disease and IgA deficiency. Instead, IgG antibodies against these same proteins would be expected to be present in a person with celiac disease. Therefore, a person suspected of having celiac disease should be checked for IgA deficiency at the time of blood testing for celiac disease to ensure that a normal test for celiac disease would not be a false negative result as a consequence of IgA deficiency.
Many studies have shown that at least half of all people with IgA deficiency have an increased rate of allergic conditions, including hay fever, asthma, eczema, hives and food allergies. Some people with IgA deficiency actually make allergic antibodies (IgE) against IgA antibodies, and are therefore at an increased risk for anaphylaxis as a result of receiving blood transfusions. Therefore, people with IgA deficiency should wear a medical alert bracelet so that if an emergency blood transfusion were necessary, a blood product free of IgA antibodies could be used in order to minimize the chance of anaphylaxis.
IgA-deficient people are also at an increased risk for various autoimmune diseases, including certain blood diseases (such as ITP, TTP and hemolytic anemia), rheumatoid arthritis, systemic lupus erythematosus, and Hashimoto’s thyroiditis. These diseases occur in approximately 20-30% of people with IgA deficiency.
Certain cancers, particularly gastrointestinal cancers and lymphomas, also occur in higher rates in people with IgA deficiency. Lastly, some people with IgA deficiency may progress to worsening forms of immunodeficiency, such as common variable immunodeficiency (CVID).
What is the Treatment for IgA Deficiency?The main treatment of IgA deficiency is the treatment of infections or of the associated diseases that may occur. People with IgA deficiency and recurring infections should be treated earlier and more aggressively with antibiotics than someone without IgA deficiency. Immunizations against common infections, such as with killed versions (live viral vaccines should be avoided) of the seasonal influenza vaccine and the pneumococcal vaccine, should be given to people with IgA deficiency. Monitoring for the occurrence of autoimmune diseases, gastrointestinal diseases, allergic conditions, cancers, and worsening immunodeficiency should also be done routinely for people with IgA deficiency.
Yel L. Selective IgA Deficiency. J Clin Immunol. 2010;30:10-16.
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