The most recent International Consensus Document (ICON) guidelines list five criteria for CVID diagnosis [10]: (1) IgG level less than two standard deviations for two measurements more than three weeks apart; (2) either low IgA or low IgM, (3) poor antibody responses to vaccination, (4) patient age above four years, (5) no secondary causes of hypogammaglobulinemia. This evidence concerns the gene CD79A and agammaglobulinemia.