Similarly Hammarstrom et al42 reported IgG3 and IgG4 compensation in an individual with IgG1 subclass antibody deficiency (IgG1ScD), and a shift in the isotype of antipolysaccharide antibodies to IgG1 and IgG3 in IgG2ScD individuals. Here, IGHG3 is linked to agammaglobulinemia.