Common Variable Immunodeficiency (CVID) is an immunological disorder, characterized by an impaired ability to produce antibodies, resulting in increased susceptibility to infections. The condition has its onset usually in young adulthood, although it may occur any time after 2-years of age. Major features of CVID include hypogammaglobulinemia, polyarthralgia, splenomegaly, increase in intestinal permeability, inflammatory bowel disease, lethargy, failure to thrive in children, and atrophy of intestinal villi resulting in malabsorption. Recurrent bacterial and viral infections are common. Both type of infections typically target the upper respiratory tract, and respond fairly well to antibiotics and antiviral therapy. Bacterial overgrowth of the intestine may also be noticed. Affected patients also show a poor titer level to vaccines.
It is believed that CVID results from defects in one of several genes, or a combination of defects in several genes. In about 20% of patients with CVID, a first degree relative has been found to have a selective IgA deficiency. There is evidence for autosomal dominant, recessive, as well as sporadic cases of CVID. However, the responsible gene(s) have been identified in only about 25% of cases with CVID. These include TACI (Tumor Necrosis Factor Receptor Superfamily, Member 13B) CD19, and ICOS (Inducible T-Cell Costimulator) genes. Family studies have also revealed a linkage of the condition to the C4A and C2 gene in the class III MHC region.
