At the same time, certain monogenic causes of the CVID phenotype (e.g., NFKB1, NFKB2, TNFSF12/TWEAK/, TNFRSF13B/TACI/, or IKZF1/IKAROS/) have been reported to cause severe viral infections individually [51, 52, 53, 54, 55]. This evidence concerns the gene TNFRSF13B and common variable immunodeficiency.