Selective Antibody Deficiency
Selective antibody deficiency is a usually acquired but sometimes hereditary immunodeficiency disorder resulting in a low level of a specific class of antibody, even though the total level of antibodies is normal.
There are several classes of antibodies (immunoglobulins). Each helps protect the body from infection in a different way (see Section 16, Chapter 183). The level of any class of antibody may be low, but the most commonly affected class is immunoglobulin A (IgA). Selective IgA deficiency usually persists throughout life. The disorder sometimes results from a chromosomal abnormality or from taking phenytoin, an anticonvulsant.
Most people with selective IgA deficiency have few or no symptoms. Others develop chronic respiratory infections, allergies, chronic diarrhea, or autoimmune disorders. If given blood transfusions or immune globulin that contains IgA, some people with selective IgA deficiency produce antibodies against IgA. Such people may have a severe allergic (anaphylactic) reaction (see Section 16, Chapter 185) the next time they are given a blood transfusion or immune globulin. They should wear a medical identification bracelet or tag to alert doctors to take precautions against such reactions.
Usually, no treatment of selective IgA deficiency is needed. Antibiotics are given to people who have recurring infections. Lifespan is usually unaffected. Selective IgA deficiency that results from taking phenytoin may resolve if the drug is discontinued.
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