vWF functions as a carrier protein for Factor VIII (the coagulation protein absent in Hemophilia A).
It promotes platelet adhesion to damaged endothelium and participates in the platelet-to-platelet cohesion necessary for thrombus formation. Together with fibronectin and collagen, vWF functions in maintaining vessel wall integrity.
Patients with severe von Willebrand disease, classified as Type 3, suffer from a complete absence of vWF in their plasma and urine. Patients with decreased circulating levels of vWF suffer from milder forms of the disease, classified as Type 1, Type 2a and Type 2b. Measurement of both vWF antigen and activity aids in the differential diagnosis of the classes of the vWF disease.