Selective IgA Deficiency

Excerpt

Immunoglobulin A (IgA) deficiency is the most common primary immunodeficiency characterized by a decreased amount of serum IgA and a concomitant lack of secretory IgA. Other immunoglobulin levels are normal. By the International Consensus definition, the diagnosis is established in individuals older than four years whose blood levels of IgA are below 7 mg/dl but have normal levels of IgG and IgM. (IgE is normal too.) These individuals have a normal antibody response to vaccines. Nevertheless, IgA deficiency should be excluded from other causes of hypogammaglobulinemia and defects in T lymphocytes. Patients who suffer from selective IgA deficiency may have clinical symptoms, but most are largely asymptomatic.

IgA deficiency is often associated with normal CD4 and CD8 T cells, with normal B lymphocytes in the systemic circulation. Some patients, though, may harbor anti-IgA autoantibodies.

Patients with IgA deficiency could also suffer from concurrent autoimmune disease. Secondary causes may be due to infection or medications, but these cases are reversible. Recent studies reveal that close to 20-30% of patients with IgA deficiency develop severe respiratory and gastrointestinal tract infections and others are at risk for developing adverse reactions to blood products. Since IgG and IgE anti-IgA antibodies may cause transfusion reactions if given whole blood, they should be administered IgA poor or washed red cells.

Without direct signs or symptoms on presentation, the diagnosis of IgA deficiency may require an initial intuitive approach with a clinical suspicion based on indirect findings.