From OMIMVon Willebrand disease is the most common inherited bleeding disorder. It is characterized clinically by mucocutaneous bleeding, such as epistaxis and menorrhagia, and prolonged bleeding after surgery or trauma. The disorder results from a defect in platelet aggregation due to defects in the von Willebrand factor protein. Von Willebrand factor is a large, multimeric protein that plays a role in platelet adhesion and also serves as a carrier for the thrombotic protein factor VIII (F8; 300841). F8 is mutated in hemophilia A (summary by Goodeve, 2010).
For a review of the various forms of von Willebrand disease, see Leebeek and Eikenboom (2016).
Classification of von Willebrand Disease
The classification of von Willebrand disease has a long and complex history. The current classification is based on that described by Sadler (1994) and updated by Sadler et al. (2006), which delineates 3 main subtypes according to the mutant protein phenotype. An earlier classification developed by a working party of the European Thrombosis Research Organization was provided by Zimmerman and Ruggeri (1983).
Von Willebrand Disease Type 1
VWD type 1 is a quantitative partial deficiency of circulating VWF. In this type of VWD, there is a normal ratio of functional VWF activity (VWF:RCo, ristocetin cofactor activity) relative to VWF antigen level (VWF:Ag) (Sadler et al., 2006, Goodeve, 2010). Mannucci (2004) stated that type 1 VWD accounts for 60 to 80% of all VWD cases and is characterized by mild to moderate quantitative deficiencies of VWF and factor VIII, which are coordinately reduced to 5 to 30% of normal plasma levels (pathogenic levels of 5 to 30 IU/dL). In an updated consensus statement, Sadler et al. (2006) noted that (1) some cases of VWF type 1 may have subtle abnormal VWF multimer patterns, but still retain normal functional activity, and (2) that loci other than VWF may be responsible for some cases of VWD.
In reviews, James and Lillicrap (2008) and Lillicrap (2009) stated that the knowledge of the pathogenesis and molecular basis of type 1 VWD is still in its infancy and still evolving. Population studies have indicated that type 1 VWD is a complex genetic trait associated with a variety of genetic and environmental factors, and that additional loci in addition to VWF are likely involved. There is still uncertainty about the pathogenicity of many identified putative VWF variants, and the incomplete penetrance and variable expressivity of type 1 disease contributes to complexity in diagnosis and understanding of disease pathogenesis.
Von Willebrand Disease Type 2
VWD type 2 (613554), which accounts for 10 to 30% of cases, is characterized by qualitative abnormalities of VWF; it is further divided into subtypes 2A, 2B, 2M, and 2N. The mutant VWF protein in types 2A, 2B, and 2M are defective in their platelet-dependent function, whereas the mutant protein in type 2N is defective in its ability to bind F8 (Mannucci, 2004; Sadler et al., 2006; Goodeve, 2010).
Von Willebrand Disease Type 3
VWD type 3 (277480), which accounts for 1 to 5% of cases, is characterized by a severe quantitative defect of VWF in plasma (less than 1% of normal plasma levels), with low but usually detectable levels of factor VIII (1 to 10% of normal plasma levels). In the rare type 3 disease (1 in 1 million people), symptoms are more frequent and severe (Mannucci, 2004, Sadler et al., 2006).
http://www.omim.org/entry/193400