Selective deficiency of IgA is the most common immune deficiency disorder. Persons with this disorder have low or absent blood levels of a special protein called immune globulin A.

IgA deficiency is inherited, which means it's passed down through families. It may be inherited as an autosomal dominant or autosomal recessive trait. It is found in approximately 1 in 700 individuals of European origin. It is less common in people of other ethnicities.

See also: Celiac disease - sprue

Persons with this condition often have chronic diarrhea caused by intestinal infections. There are often frequent ear, sinus, and lung infections.

Other symptoms include mouth infections and unexplained asthma or bronchiectasis.

There may be a family history of IgA deficiency. Tests that may be done include:

• Serum immunoelectrophoresis
• Quantitative immunoglobulins (serum IgA extremely low or absent)