In a large series of CLL patients, subclass deficiency (particularly IgG3 and IgG1 subclass deficiency) better correlated with recurrent or significant infections than hypogammaglobulinemia itself (100% of IgG subclass deficiency versus 50% of hypogammaglobulinemia, respectively) (52). This evidence concerns the gene IGHG3 and agammaglobulinemia.