Von Willebrands disease (VWD) is a hereditary deficiency of von Willebrands factor (VWF), which causes platelet dysfunction. Von Willebrands factor (VWF) is synthesized and secreted by vascular endothelium to form part of the perivascular matrix. VWF promotes the platelet adhesion phase of hemostasis by binding with a receptor on the platelet surface membrane (glycoprotein Ib-IX), which connects the platelets to the vessel wall. VWF is also required to maintain normal plasma factor VIII levels. Von Willebrands disease (VWD) is classified into 3 types; Type 1: a quantitative deficiency of VWF, which is the most common form and is an autosomal dominant disorder; Type 2: a qualitative impairment in synthesis of VWF that can result from various genetic abnormalities and is an autosomal dominant disorder; and Type 3: a rare autosomal recessive disorder in which homozygotes have no detectable VWF. The disease is characterized by an increased bleeding time, a prolonged partial activated thromboplastin time and excessive mucosal and cutaneous hemorrhage following minor injury. Levels of VWF can also temporarily increase in response to stress, exercise, pregnancy, inflammation, or infection. Rarely, VWD may be due to an acquired VWF deficiency, where there is no family or personal bleeding history up to the point of presentation. It is sometimes seen in patients with pulmonary hypertension and structural defects of the heart (such as aortic valve stenosis), lymphoma, myeloma, or autoimmune disorders (such as systemic lupus erythematosus) that cause the production of VWF antibodies, myeloproliferative disorders associated with increased platelet production that cause increased platelet binding, and hypothyroidism, which can decrease VWF production. See Factor VIII:C, Plasma