IgA deficiency is an IgA level < 10 mg/dL with normal IgG and IgM levels. It is the most common primary immunodeficiency. Many patients are asymptomatic, but some develop recurrent infections and autoimmune disorders. Some patients develop common variable immunodeficiency, and some remit spontaneously. Diagnosis is by measuring serum Igs. Treatment is avoidance of blood products that contain IgA; antibiotics are given as needed.
IgA deficiency affects up to 1/333 people. Transmission is autosomal dominant with incomplete penetrance. IgA deficiency is commonly associated with certain HLA haplotypes, and rare alleles or deletions of genes in the major histocompatibility complex (MHC) class III region (see Biology of the Immune System: Human Leukocyte Antigen (HLA) System) are common. IgA deficiency also occurs in siblings of children with common variable immunodeficiency (CVID) and evolves into CVID in some patients. Use of drugs such as phenytoin, sulfasalazine, colloidal gold and d-penicillamine may lead to IgA deficiency in genetically susceptible patients.
Symptoms and Signs
Many patients are asymptomatic; others have recurrent sinopulmonary infections, diarrhea, allergies, or autoimmune disorders (eg, celiac or inflammatory bowel disease, SLE, chronic active hepatitis). Anti-IgA antibodies may develop after exposure to IgA in transfusions; anaphylactic reactions to IV immune globulin (IVIG) and other blood products that contain IgA may occur.
Diagnosis is suspected in patients who have recurrent infections (including giardiasis); anaphylactic transfusion reactions; or a family history of CVID, IgA deficiency, or autoimmune disorders or who are taking drugs that lead to IgA deficiency. Diagnosis is confirmed by a serum IgA level < 10 mg/dL with normal IgG and IgM levels and normal antibody titers in response to vaccine antigens.
A few IgA-deficient patients develop CVID over time; others improve spontaneously. Prognosis is worse if an autoimmune disorder develops.
Treatment is avoidance of blood products that contain IgA because even trace amounts can elicit an anti-IgA–mediated anaphylactic reaction. If RBC transfusion is needed, only washed RBCs or frozen blood can be used.
Antibiotics are given as needed for bacterial infections of the ears, sinuses, lungs, or GI or GU tract.
IVIG is contraindicated because many patients have antibodies to IgA and because IVIG is > 99% IgG, which patients do not need. Patients are advised to wear an identification bracelet to prevent inadvertent plasma or IVIG administration, which could lead to anaphylaxis.
Last full review/revision September 2008 by Rebecca H. Buckley, MD
Content last modified February 2012