Genome-wide association studies (GWASs) in IgAN support that galactose-deficient IgA1 (Gd-IgA1) is heritable (3, 4), and they also suggest that some GWAS loci, such as CARD9, TNFSF13, and PSMB8, are shared among IgAN, inflammatory bowel disease (IBD), and bacterial infections (5). Here, TNFSF13 is linked to inflammatory bowel disease.