Von Willebrand disease type II (vWD II)

Von Willebrand disease of type II is a hereditary bleeding disorder. It causes much more severe bleeding that the vW type 1 and if there is no direct injury, it is very difficult to find out, whether the dog is a carrier of this mutation and affected by this disease.  The blood plasma contains von Willebrand factor (VWF) that is responsible for the correct blood clotting.  However, problems occur, if the level of von Willebrand factor is low or the activity of vW factor decreases.

vW factor is produced by vascular endothelial and subendothelial cells and megakaryocytes and circulates in blood plasma and forms the largest protein molecules. The main function of vWF is to ensure the stabilisation of the coagulation factor VIII and facilitate the adhesion of blood plateles to blood vessel subendothelial cells. In affected individuals, severe bleeding conditions occur, particularly after a traumatic accident or injury. In particular, pointers used for hunting represent a high-risk group as the possibility of the injury is very high. This specific type of disease occurs primarily in German Shorthaired Pointers, German Wirehaired Pointers and Boykin Spaniels.

Mutation that causes vWD II is inherited as an autosomal recessive trait, which is associated with a mutation c.4937A>G in vWD gene. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive /negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

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References:

Kramer, J. W., et al. "A von Willebrand's factor genomic nucleotide variant and polymerase chain reaction diagnostic test associated with inheritable type-2 von Willebrand's disease in a line of German shorthaired pointer dogs." Veterinary Pathology Online 41.3 (2004): 221-228.

Gavazza, Alessandra, et al. "Estimated prevalence of canine type 2 von Willebrand disease in the Deutsch-Drahthaar (German wirehaired Pointer) in Europe." Research in Veterinary science 93.3 (2012): 1462-1466.