Many studies have considered variants in NFKB1 as a monogenic cause of CVID, and considered heterozygous loss-of-function variants in NFKB1 to be the most common known monogenic cause of CVID (Fliegauf et al., 2015; Kaustio et al., 2017; Tuijnenburg et al., 2018). This evidence concerns the gene NFKB1 and common variable immunodeficiency.