Although the pathogenesis of selective IgA deficiency (SIgAD) is poorly understood, inheritance patterns suggest it is autosomal dominant. Despite this fact, first-degree family members of patients diagnosed with SIgAD are not routinely screened for primary immunodeficiency, due in part to lack of symptomatology. We wish to present a case in which two asymptomatic adult children of a 45 year old white female with SIgAD were screened and found to have both IgA deficiency and anti-IgA antibodies.

Bloodwork was first performed on the mother, and later on her children, and consisted of quantitative total serum Ig levels (IgM, IgG, IgA), serum IgE, IgG subtypes, anti-IgA antibody levels, humoral immune panel (diphtheria antitoxoid antibody, tetanus antitoxoid antibody, and a 6 serotype pneumococcal antibody panel), and a CBC with WBC count differential.

The mother's bloodwork revealed a total serum IgA level of <13mg/dL (normal 81 to 463mg/dL). Her son, age 20, had an IgA level of <14mg/dL with a borderline low IgM level of 39mg/dL (normal 48 to 271mg/dL), and her daughter, age 22, had an IgA level of 33mg/dL, suggesting a relative deficiency of serum IgA. Additionally, each child had detectable anti-IgA antibodies of the IgG isotype. All other remaining lab results were unremarkable.

In order to decrease the morbidity and mortality of patients with SIgAD and/or carriers of anti-IgA antibodies, first-degree family members of individuals diagnosed with SIgAD should be routinely screened for primary immunodeficiency, regardless of their level of symptomatology.