Recent studiesperformed in the European Union, the UK, and Canadahave provided some data on the molecular pathology oftype 1 vWD and established that there is a genotype-phenotypecorrelation [80,81,82]; the vWF gene was analyzed in~300 type 1 vWD patients in the 3 studies, which demonstratedthat both allelic and locus heterogeneity should beconsidered to play a role in the molecular pathogenesis oftype 1 vWD. This evidence concerns the gene VWF and von Willebrand disease (hereditary or acquired).