Molecular Genetics of von Willebrand Disease

Abstract

IntroductionVon Willebrand disease (vWD) is a common inherited bleeding disorder that is notable for a high degree of variability in clinical presentation and the considerable heterogeneity of its molecular basis. Confusion about the genetic origin of this disorder has existed since its original description by Eric von Willebrand in 1926.1 Dr. von Willebrand coined the term “pseudohemophilia” to describe the disease in the original pedigree. Though it resembled the bleeding diathesis of hemophilia, von Willebrand also noted findings suggesting an abnormality in platelet function. The severity of bleeding in this family varied widely from mild bleeding to severe hemorrhage, the latter resulting in the death of the proband at the time of her fourth menstrual period.Von Willebrand incorrectly characterized the inheritance pattern in the original Åland Island pedigree as X-linked dominant, because of the apparent greater frequency of the disease in female patients. Now, it is recognized that the greater frequency was largely by chance and due to increased penetrance related to the hemostatic stresses of menstruation and pregnancy. Nonetheless, von Willebrand clearly distinguished the inheritance pattern of vWD from that of classic hemophilia. It is now known that vWD is due to either quantitative or qualitative defects in von Willebrand factor (vWF), encoded by a gene on chromosome 12, whereas hemophilia is due to mutations in the factor VIII gene on the X chromosome.2