Selective immunoglobulin deficiency is a congenital immunodeficiency disorder resulting 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. Each class helps protect the body from infection in a different way (see Biology of the Immune System: Antibodies). The level of any class may be low, but the most commonly affected class is immunoglobulin A (IgA).

Selective IgA Deficiency: This disorder usually persists throughout life. The disorder sometimes results from a chromosomal abnormality. If people have a genetic makeup that makes them susceptible, the deficiency may result from taking phenytoin (an anticonvulsant), sulfasalazine (an antibiotic), or gold compounds or penicillamine (used to treat rheumatoid arthritis). The deficiency also occurs in family members of people with common variable immunodeficiency.

Most people with selective IgA deficiency have few or no symptoms. Others develop chronic lung infections, sinusitis, allergies, chronic diarrhea, or autoimmune disorders, such as inflammatory bowel disease or systemic lupus erythematosus (lupus). A few people develop common variable immunodeficiency.

If given standard blood transfusions or immune globulin infusions (both of which normally contain IgA), some people with selective IgA deficiency produce antibodies against IgA. The next time such people are given a blood transfusion or immune globulin, they may have a severe allergic (anaphylactic) reaction (see Allergic Reactions and Other Hypersensitivity Disorders: Anaphylactic Reactions). They should wear a medical identification bracelet or tag to alert doctors to take precautions against such reactions.

Some people improve spontaneously. Life span is usually unaffected unless an autoimmune disorder or common variable immunodeficiency develops.

Doctors suspect the deficiency in people with many infections, especially if they are taking drugs that can cause it or if they have other associated disorders. 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 recurring infections. Selective IgA deficiency that results from taking a drug may resolve if the drug is stopped, but this does not happen very often.

Last full review/revision September 2008 by Rebecca H. Buckley, MD