|Indicated in the investigation of immunodeficiency, lymphoproliferative disease, recurrent infections and “failure to thrive”.
Reduced Ig levels may be caused by increased loss (protein-losing enteropathy, nephrotic syndrome), reduced synthesis (lymphoproliferative disorders, primary immunodeficiency) and increased catabolism.
IgA deficiency is the commonest primary immunodeficiency disease, occurring in about 1 in 700 Caucasians.
It may be asymptomatic, or associated with recurrent infections.
Anti-IgA antibodies may be present in IgA deficiency.
Polyclonal elevation of Igs occurs in chronic infections, chronic inflammation, liver disease and autoimmune disease.
Very high levels may be seen in chronic active hepatitis, HIV infection, Sjogren’s Syndrome and sarcoidosis.
Polyclonally elevated IgA is seen in cirrhosis and polyclonally elevated IgM in primary biliary cirrhosis.