von Willebrand disease (vWD) is a bleeding disorder resulting from an autosomally inherited defect that causes a deficiency, or absence, of von Willebrand factor. This disease is associated with impaired platelet adhesion and epistaxis, as well as increased blood loss from trauma, surgery, menorrhagia, or postpartum bleeding.

The incidence of this clinically significant disease is estimated at approximately 125:1,000,000. The incidence of severe vWD is estimated at approximately 0.5:1,000,000 to 5:1,000,000. There are no observed racial or gender predilections.

vWD is an inherited defect in the von Willebrand factor gene, which is located on the short arm of chromosome 12. It is divided into three major types: Type I: partial quantitative deficiency; Type II: qualitative deficiency; and Type III: total deficiency. The types are differentiated by molecular mechanisms resulting from differences in the von Willebrand factor gene mutation and its expression.