Von willebrand disease

[Marquetta]

Von Willebrand disease is a hereditary deficiency or abnormality of the blood protein von Willebrand factor, which affects platelet function.
(See also Overview of Platelet Disorders and Overview of Thrombocytopenia.)
The von Willebrand factor is found in plasma, platelets, and the walls of blood vessels. Platelets are cells that are made in the bone marrow and circulate in the bloodstream and help blood clot. When the von Willebrand factor is missing or defective, platelets cannot adhere to the vessel wall at the site of an injury. As a result, bleeding does not stop as quickly as it should.
Platelets are cells that circulate in the bloodstream and help blood clot. The blood usually contains about 140,000 to 440,000 platelets per microliter (140