Selective immunoglobulin A deficiency
Selective immunoglobulin A (IgA) deficiency (SIgAD) is a relatively mild genetic immunodeficiency. 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. It is the most common of the primary antibody deficiencies.