Variants in the gene TNFRSF13B have been associated with the common variable immunodeficiency (CVID) syndrome “Common variable immune deficiency 2” (CVID2, OMIM # 240500), and the immunoglobulin A deficiency (IGAD) “Immunoglobulin A deficiency 2”/IGAD2 (OMIM # 609529). Here, TNFRSF13B is linked to immunoglobulin A deficiency 2.