von Willebrand Disease, named after the Finnish physician who discovered it, is a bleeding disorder caused by the deficiency of a blood clotting protein called von Willebrand Factor, which is necessary in the initial stages of blood clotting. This glue-like protein interacts with platelets to form a plug that prevents more blood from continuing to flow to the injury.
von Willebrand is estimated to occur in 1% to 2% of the population. People with von Willebrand Disease fall into one of the following classifications:
Type 1: This is the most common and mildest form of von Willebrand Disease. Levels of von Willebrand factor are lower than normal, and levels of factor VIII may also be reduced.
Type 2: There is a defect in the structure of the von Willebrand protein that causes lower than normal VW factor protein activity.
- Type 2a - the level of VW factor is reduced, as is the ability of platelete to clump together
Type 2b – although the VW factor is defective, the ability for platelets to clump together is actually increased.
Type 2m – the VWF is not able to stick to the platelets and therefore a platelet plug is not properly formed.
Type 2n – Also called type 2 Normandy. Type 2n occurs when there isn’t enough VWF to carry the factor VIII protein to the site of injury and therefore there are decreased levels of factor VIII to form a fibrin clot.
Type 3: This is the most severe form of von Willebrand disease. There is a total absence of von Willebrand factor, and factor VIII levels are often less than 10%.
Pseudo (or platelet-type) von Willebrand disease: This disorder resembles Type 2b von Willebrand disease, but the defects appear to be in the platelets rather than the von Willebrand factor.