How is von Willebrands disease inherited?
The most common form (Type I vWD) is thought to be an autosomal trait with incomplete dominance. This means offspring may inherit the disorder if either parent carries the gene, but not all offspring will be affected to the same extent. Dogs with type I disease have reduced but measurable levels of Von Willebrand factor (1 to 60 per cent). Animals that inherit the gene for type I vWD from both parents (homozygotes) die before birth or shortly thereafter. Type III vWD is relatively rare. This form is autosomal recessive. Animals are only affected if they inherit the abnormal gene from both parents, who are clinically unaffected carriers. Affected dogs have zero levels of vWF, while carrier parents have 15 to 60 per cent of normal levels. Type II vWD is very rare. It is an autosomal recessive trait. Bleeding abnormalities are severe in dogs with Types II and III von Willebrand’s disease. What breeds are affected by von Willebrand’s disease? Type I vWD: This is by far the most common form
