TNFRSF13B and selective IgA deficiency disease: Neither TNFRSF13B nor TNFSF13 harboured significantly associated SNPs in our SIgAD analyses, but the association of SNPs in both with serum IgA, the genetic correlation between serum IgA and SIgAD, and the functions of this signalling pathway suggest larger GWAS might find SIgAD-associated variants in these genes.