von Willebrand disease is a defect of

Primary hemostasis: the formation of the platelet plug.Disruption of the endothelium exposes subendothelial von Willebrand factor (vWF) and collagen, which promote platelet adherence and activation. Activation of platelets results in a dramatic shape change as well as the release of secretory granules. Within minutes the secreted products recruit additional platelets, which undergo aggregation to form a primary hemostatic plug.Defects of primary hemostasis (platelet defects or von Willebrand disease) often present with small bleeds in the skin or mucosal membranes. These bleeds typically take the form of petechiae, minute 1 to 2 mm hemorrhages, or purpura, which are slightly larger (>=3 mm) than petechiae. Mucosal bleeding associated with defects in primary hemostasis may take the form of epistaxis (nosebleeds), gastrointestinal bleeding, or excessive menstruation (menorrhagia).Ref: Robbins and Cotran Pathologic; 9th edition; Chapter 4; Hemodynamic Disorders, Thromboembolic Disease, and Shock; Page no: 122