Selective Immunoglobulin Deficiency
(See also Overview of Immunodeficiency Disorders.)
Selective immunoglobulin deficiency is usually inherited. It results in a low level of one type (class) of antibody (immunoglobulin), even though the levels of other immunoglobulins are normal.
There are several classes of immunoglobulins, such as immunoglobulin A (IgA), IgD, IgE, IgG, and IgM. Each class helps protect the body from infection in a different way (see Acquired Immunity : Antibodies).
The level of any immunoglobulin class may be low, but the most commonly affected class is IgA.
Selective IgA deficiency results in a low level of immunoglobulin A (IgA). Levels of IgG and IgM are normal.
Selective IgA deficiency is the most common immunoglobulin abnormality. It may be caused by a mutation in a specific gene or by a drug, such as phenytoin (used to treat seizure disorders) or sulfasalazine (used to treat rheumatoid arthritis). How the gene mutation is inherited is unknown, but having a family member with selective IgA deficiency increases the risk by about 50 times
Most people with selective IgA deficiency have few or no symptoms. Others develop chronic lung infections, sinusitis, allergies, asthma, nasal polyps, chronic diarrhea, or, rarely, autoimmune disorders, such as systemic lupus erythematosus (lupus) or inflammatory bowel disease (which usually causes gastrointestinal symptoms that often recur or that may be serious). A few people develop common variable immunodeficiency over time.
Some people with selective IgA deficiency produce antibodies against IgA if they are exposed to IgA in blood transfusions or immune globulin (antibodies obtained from the blood of people with a normal immune system). Rarely, antibodies against IgA trigger a severe allergic (anaphylactic) reaction the next time such people are given a blood transfusion or immune globulin.
Some people improve spontaneously. Life span is usually unaffected. If an autoimmune disorder or another immune disorder (such as common variable immunodeficiency) develops, life span may be shortened.
Doctors suspect selective IgA deficiency in people if they have
Blood tests to measure immunoglobulin levels are done to confirm the diagnosis.
Usually, no treatment of selective IgA deficiency is needed.
Antibiotics are given to people who have an infection. If the disorder is severe, antibiotics are given in advance to prevent infections from developing.
People who have had an anaphylactic reaction to a blood transfusion or immune globulin should wear a medical identification bracelet or tag to alert doctors to take precautions against such reactions.
Selective IgA deficiency that results from taking a drug usually resolves if the drug is stopped.