Other reported associations include X-linked agammaglobulinemia, selective IgM or IgG deficiency, and rarer entities such as selective IgE deficiency, unclassified hypogammaglobulinemia, specific antibody deficiency, specific polysaccharide antibody deficiency, and heavy- or light-chain deficiencies. This evidence concerns the gene CD40LG and isolated agammaglobulinemia.