Most severe cases of type 1 VWD are caused by mutations in theVWFgene, and often patients with moderately reduced levels of VWF do not have a mutation in theVWFgene.2A previously published genome-wide association study (GWAS) identified eight genes that contribute to plasma level variation of VWF.3TheABOgene showed the strongest effect, but smaller effects were seen for theVWF,STXBP5,STAB2,SCARA5,STX2,TC2N, andCLEC4Mgenes. Here, VWF is linked to von Willebrand disease 1.