Von Willebrand disease type III (vWDIII) (kooikerhondje type) is an inherited bleeding disorder affecting dogs. Dogs affected with VWDIII (kooikerhondje type) have extremely low or undetectable levels of von Willebrand coagulation factor (vWf), which is an essential protein needed for normal blood clotting. Affected dogs bruise easily, have frequent nosebleeds, bleed from the mouth spontaneously or when juvenile teeth are lost, and experience prolonged bleeding after surgery or trauma. The bleeding may be severe enough to cause death. Dogs that have one copy of the Mutation (carriers) also have decreased amounts of vWf but there is variability in the levels such that not all carriers are equally affected. Dogs that have less than 35% of the normal amount of vWf have mild to moderate signs of a bleeding disorder. Due to the variable severity of the disorder, Carrier dogs may not be identified until a surgery is performed or trauma occurs at which time excessive bleeding is noted. However, most carrier dogs will not show symptoms of increased bleeding. Veterinarians performing surgery on known affected or carrier dogs should have ready access to blood banked for transfusions. Most carrier dogs will have a normal lifespan with this condition despite the possibility of having increased blood clotting times. Affected dogs may develop life-threatening bleeding with an accidental injury or any surgical procedure.
Genetic testing of the VWF gene will reliably determine whether a dog is a genetic Carrier of von Willebrand disease III (kooikerhondje type). Von Willebrand disease III (kooikerhondje type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. Carrier dogs can have mild features of the disease but when bred with another carrier of the same Mutation, there is a risk of having severely affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the VWF gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
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van Oost BA, Versteeg SA, Slappendel RJ. DNA testing for type III von Willebrand disease in Dutch kookier dogs. J Vet Intern Med. 2004 May-Jun;18(3):282-8.