In this illustration of the normal clotting process, a tear in the vascular endothelium is being plugged by platelets (blue/white) bound to Factor VIII coagulation molecules (yellow) that are sequestered by von Willebrand protein (white threads), acting to tie the clot together. Von Willebrand disease (VWD) is considered to be the most prevalent bleeding disorder, affecting 1% of the US population. It is associated with excessive bruising, bleeding, and in women, menorrhagia. VWD can be caused by a number of defects or deficiencies of von Willebrand protein, a clotting factor involved in stabilization of the Factor VIII coagulation molecule and platelet adhesion.