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Selective IgA Deficiency
Selective IgA deficiency is an IgA level < 7 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 over time, and some remit spontaneously. Diagnosis is by measuring serum Igs. Treatment is antibiotics as needed (sometimes prophylactically) and usually avoidance of blood products that contain IgA.
IgA deficiency prevalence ranges from 1/100 to 1/1000. The inheritance pattern is unknown, but having a family member with selective IgA deficiency increases the risk by about 50 times.
Some patients have mutations in the TACI (transmembrane activator and calcium-modulator and cyclophilin ligand interactor) gene. Selective IgA deficiency is also commonly associated with certain HLA haplotypes; rare alleles or deletions of genes in the major histocompatibility complex (MHC) class III region (see page Human Leukocyte Antigen (HLA) System) are common.
Drugs such as phenytoin, sulfasalazine, gold, and d-penicillamine may lead to IgA deficiency in some patients.
Most patients are asymptomatic; others have recurrent sinopulmonary infections, diarrhea, allergies (eg, asthma, associated nasal polyps), or autoimmune disorders (eg, celiac or inflammatory bowel disease, SLE, chronic active hepatitis).
Anti-IgA antibodies may develop after exposure to IgA in transfusions, IV immune globulin (IVIG), or other blood products; rarely, if reexposed to these products, patients may have anaphylactic reactions.
Diagnosis is suspected in patients who have recurrent infections (including giardiasis), anaphylactic transfusion reactions, or a family history of common variable immunodeficiency (CVID), IgA deficiency, or autoimmune disorders or who are taking drugs that lead to IgA deficiency. Diagnosis is confirmed by a serum IgA level < 7 mg/dL with normal IgG and IgM levels and normal antibody titers in response to vaccine antigens.
Testing of family members is not recommended because most patients with low IgA have no clinically significant manifestations.
Allergic manifestations are treated. Antibiotics are given as needed for bacterial infections of the ears, sinuses, lungs, or GI or GU tract and, in severe cases, are given prophylactically.
Blood products that contain IgA are avoided because even trace amounts can elicit an anti-IgA–mediated anaphylactic reaction. If RBC transfusion is needed, only washed packed RBCs can be used.
Because IVIG contains mostly IgG, patients with IgA deficiency do not benefit from IVIG; also, anaphylactic reactions are a risk because patients may have developed anti-IgA antibodies. Rarely, if patients have no antibody response to vaccines and if prophylactic antibiotics are ineffective, specially formulated IVIG preparations that contain extremely low levels of IgA can be tried and may be somewhat effective.
Patients are advised to wear an identification bracelet to prevent inadvertent plasma or IVIG administration, which could lead to anaphylaxis.
Selective IgA deficiency is the most common primary immunodeficiency.
Patients may be asymptomatic or have recurrent infections or autoimmune disorders; some develop CVID over time, but in others, selective IgA deficiency spontaneously resolves.
Suspect selective IgA deficiency if patients have anaphylactic reactions to transfusions, take drugs that lead to IgA deficiency, or have recurrent infections or a suggestive family history.
Confirm the diagnosis by measuring Ig levels and antibody titers after vaccines are given; an IgA level < 7mg/dL and normal IgG and IgM levels and antibody titers are diagnostic.
Give antibiotics as needed and, in severe cases, prophylactically.
Avoid giving patients blood products that contain IgA.
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