Type 2B von Willebrand's disease in thirteen individuals from five unrelated Australian families: phenotype and genotype correlations

Type 2B von Willebrand's disease (VWD) is due to a qualitative defect in von Willebrand factor (VWF) in which there is an increased affinity for the platelet glycoprotein Ib-IX-V receptor complex. Spontaneous binding of type 2B VWF to platelets and subsequent clearance from the plasma is thought to account for the characteristic phenotype of type 2B VWD. These gain-of-function mutations are due to single amino substitutions that are clustered within the functionally important A1 domain of VWF. We describe 13 individuals from five unrelated families in Australia with type 2B VWD, report their phenotypic abnormalities, and delineate their causative mutations. We confirm that the mutation Arg543Trp is also particularly common among families with type 2B VWD in Australia.