IgA deficiency
| Selective immunoglobulin A deficiency | |
|---|---|
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| The dimeric IgA molecule. 1 H-chain, 2 L-chain, 3 J-chain, 4 secretory component | |
| Classification and external resources | |
| Specialty | hematology |
| ICD-10 | D80.2 |
| ICD-9-CM | 279.01 |
| OMIM | 137100 |
| DiseasesDB | 29569 |
| MedlinePlus | 001476 |
| eMedicine | med/1159 |
| MeSH | D017098 |
Selective immunoglobulin A (IgA) deficiency (SIgAD) is a genetic immunodeficiency, a type of hypogammaglobulinemia. People with this deficiency lack immunoglobulin A (IgA), a type of antibody that protects against infections of the mucous membranes lining the mouth, airways, and digestive tract. It is defined as an undetectable serum IgA level in the presence of normal serum levels of IgG and IgM, in persons older than 4 years. It is the most common of the primary antibody deficiencies. Most such persons remain healthy throughout their lives and are never diagnosed.
‘85–90% of IgA-deficient individuals are asymptomatic’, although the reason for lack of symptoms is relatively unknown and continues to be a topic of interest and controversy. ‘Some patients with IgA deficiency have a tendency to develop recurrent sinopulmonary infections, gastrointestinal infections and disorders, allergies, autoimmune conditions, and malignancies’. These infections are generally mild and would not usually lead to an in-depth workup except when unusually frequent. They may present with severe reactions including anaphylaxis to blood transfusions or intravenous immunoglobulin due to the presence of IgA in these blood products. Patients have an increased susceptibility to pneumonia and recurrent episodes of other respiratory infections and a higher risk of developing autoimmune diseases in middle age.
Although it has some similarities to common variable immunodeficiency (CVID), it does not present the same lymphocyte subpopulation abnormalities. It may anyway progress to CVID.
Those patients with selective immunoglobulin A deficiency may be prone to recurrent infections when on hemodialysis.
When suspected, the diagnosis can be confirmed by laboratory measurement of IgA level in the blood. SigAD is an IgA level < 7 mg/dL with normal IgG and IgM levels (reference range 70-400mg/dl for adults; children somewhat less).
Selective IgA deficiency is inherited and has been associated with differences in chromosomes 18, 14 and 6. The afflicted person usually has no other family members with the disorder.
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