Von Willebrand disease type 3 (VWD3)
Von Willebrand disease (vWD) is a bleeding disorder of variable severity that results from a quantitative or qualitative defect in von Willebrand factor (vWF). On vascular injury, vWf mediates platelet adhesion to exposed subendothelium and is involved in platelet-to-platelet aggregation. The disease is the most common hereditary bleeding disorder and it is genetically and clinically heterogeneous. Clinical signs of the disease include spontaneous bleeding from mucosal surfaces and excess blood loss after surgery or trauma. Three clinical types, 1, 2, and 3, have been described.
Von Willebrand disease type 3 is the severest form of the disease. It is inherited as an autosomal recessive trait, and affected individuals have no detectable vWF in their blood. Serious bleeding episodes require transfusions of blood or cryoprecipitate to supply the missing vWF. Heterozygous carriers have moderately reduced factor concentrations but generally appear to have normal hemostasis.
Testing of affected dogs can be done by von Willebrand disease type 3 antigen testing or by coagulation assays, but these procedures yield variable results. This variability makes it difficult for breeders to use this information to eliminate the disease-causing allele from their lines. Thus, it is highly desirable that DNA tests are run to get definitive answers.
Moser, J., Meyers, K.M., Meinkoth, J.H., and Brassard, J.A. (1996). Temporal variation and factors affecting measurement of canine von Willebrand factor. American Journal of Veterinary Research 57, 1288–1293.