inherited blood disorder (blood disease) characterized by a prolonged bleeding time and a deficiency of factor VIII, an important blood-clotting agent. This disorder is due to deficiencies in von Willebrand factor (vWF), a molecule that facilitates platelet adhesion and is a plasma carrier for factor VIII. Symptoms usually include abnormal bruising, bleeding from mucosal surfaces such as the gums and the gastrointestinal tract, and prolonged bleeding from any break in the skin or during surgery. The level of vWF and the severity of the disease vary over time, often as a result of hormonal or immune responses.

Von Willebrand disease types 1 and 2 are milder forms and are inherited as autosomal dominant traits; type 3, the most severe form, is recessive and requires that the trait be inherited from both parents. The disease is treated with desmopressin (DDAVP), a drug that increases levels of factor VIII and vWF, or plasma-derived factor VIII preparations. See also thrombocytopathy.