von Willebrand disease (VWD) is a disorder that is caused by a problem with one of the proteins in the blood (von Willebrand factor or vWF). People with VWD either don’t have enough vWF or what they have doesn’t work properly.
vWF plays 2 important roles in blood clotting. It makes platelets stick to the wall of an injured blood vessel and to each other. Without it, a platelet plug cannot be made. vWF is also a called a carrier protein because it carries one of the clotting factors, factor VIII (8), with it. This means that it helps make sure there is enough factor VIII (8) in the blood and that it gets to where it’s needed. Without vWF, factor VIII (8) will be broken down in the bloodstream and there may not be enough of it to stop bleeding.
There are several different classifications of VWD. These includes:
- Type 1: A person with Type 1 VWD has lower-than-normal levels of vWF and may also have low levels of factor VIII, which is another type of blood-clotting protein. Body makes normal amounts of vWF but it does not work the way it should.
- Type 2 VWD is further broken down into 4 subtypes—2A, 2B, 2M, and 2N—depending on the specific problem with the person’s vWF. Each type is treated differently:
- Subtype 2A: vWF levels are reduced, as is the ability of platelets to clump together
- Subtype 2B: Although the factor itself is defective, the ability of platelets to clump together is actually increased
- Subtype 2M: vWF levels are decreased and the interaction of vWF with platelets or connecting tissue is reduced
- Subtype 2N: Binding of vWF to factor VIII (8) is markedly decreased
- Type 3: Most severe form of VWD; a person has very little or no vWF and low levels of factor VIII (8)