Von Willebrand disease type III (vWDIII) is an inherited bleeding disorder affecting dogs. Dogs affected with VWDIII 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.

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