Definition:

There are three major categories of antibody deficiencies: (a) defects in early B cell development, (b) hyper-IgM syndromes (also called class switch recombination defects), and (c) common variable immunodeficiency (CVID). Category (c) CVID, also called acquired hypogammaglobulinemia, adult-onset hypogammaglobulinemia, or dysgammaglobulinemia, is a heterogeneous group of disorders involving both B-cell and T-cell immune function, the predominant manifestation of which is hypogammaglobulinemia. CVID is characterized by recurrent bacterial infections, decreased serum Ig levels, and abnormal antibody responses. The mutated genes that produce the CVID phenotype are known only for a minority of patients, and they are diverse in their influence on immune function. Homozygous mutations in ICOS are clearly the cause of disease. Heterozygous mutations in the TNF receptor family member TACI (transmembrane activator and calcium-modulating cyclophilin ligand interactor) can be found in up to 10% of patients with CVID.