Von Willebrand Disease I (vWDI)

Von Willebrand's disease (vWD) is the most common hereditary bleeding disorder in dogs as well as in human. vWD is caused by partial or full absence of von Willebrand factor (vWF) or his unfunctionality due to structural abnormality. von Willebrand factor is multimeric plasma glycoprotein which plays a major role in haemostasis, the body response on blood vessel damage and bleeding. vWF protein is required for normal platelet adhesion at sites of vessel injury and promotes the platelet aggregation. In addition, it also stabilizes blood coagulation factor VIII (FVIII). Characteristic vWD clinical signs are: rapid occurrence of prolonged and persistent bleedings at sites of minor skin injuries and venipuncture, spontaneous mucosal bleeding from nasal cavity, intestines and gums, postoperative and posttraumatic injuries... Despite the vWF importance in blood clotting partial or complete absence of vWF from blood is not always lethal, as well as the vWD can remain unnoticed for years. Affected individuals may experience light, moderate or serious bleedings since vWD is genetically and clinically heterogeneous disease. In dogs, three types of von Willebrand's disease are occurring, and different mutations in the VWF gene are responsible for quantitative and qualitative vWF properties which are the basis for dividing vWD into vWD type I (partial absence of vWF), II (unfunctional vWF) and III (complete absence of vWF).

von Willebrand's disease type I (vWD I), occurring in many dog breeds, is the most common form of vWD found in most mammals. vWD type I is characterized by mild to moderate bleeding tendency due to constant deficiency of otherwise completely functional plasma vWF and although in general is less severe than types II and III serious bleeding can occur.

vWD is generally diagnosed by ELISA test detecting vWF antigen and is used only when bleeding occurs. In addition, it is always not possible to determine the genetic status of the animals due to the temporal variations in the amount of plasma vWF, therefore, the ELISA test is not a reliable test. The only reliable method for determining the genotype for vWD is a genetic diagnostic test, which determines the variant alleles of VWD gene that accurately differentiate between clear, carrier and affected dogs.

Inheritance: autosomal recessive

Mutation: VWF gene

Genetic test: The method used for testing is extremely accurate and allows complete differentiation between affected animals, carriers and healthy dogs. Testing can be done at any age.