Occurrence: 1 in 500 to 700 Caucasians from Northern Europe, less common in other ethnic groups
Clinical features: most patients are asymptomatic and unsuspected
Conditions that may be found in a patient with IgA deficiency:
(1) atopic skin disorders
(2) frequent upper and lower respiratory tract infections
(3) allergic rhinitis
(4) food allergies, including mild allergies
(5) pernicious anemia
(6) Giardiasis
(7) bacterial overgrowth syndrome in the upper GI tract
(8) celiac disease
(9) common variable immunodeficiency
(10) increased risk for Crohn's disease or ulcerative colitis
(11) increased risk for autoimmune disease
(12) occasionally anaphylactic reactions on exposure to IgA in blood products
Concurrent genetic abnormalities may include:
(1) ataxia telangiectasia
(2) defects in chromosome 18
Laboratory features:
(1) serum IgA concentration < 0.06 g/L (patients with a partial IgA deficiency may show a higher concentration that is still below the lower limit of the normal reference range)
(2) normal total serum concentrations of IgG and IgM
(3) Some patients have a deficiency of IgG2, IgG3 and/or IgG4 (underlies the higher rate of respiratory and other infections)
(4) anti-IgA antibodies in those who produce absolutely no IgA
Differential diagnosis:
(1) There may be a delay in IgA production in early childhood. The diagnosis of selective IgA deficiency is not made until the child is at least 2 years old (some use 5 years) old.
(2) Acquired IgA deficiency associated with drug therapy or certain viral infections.
