VWF and von Willebrand disease (hereditary or acquired): von Willebrand disease (VWD) is the most common inherited bleeding disorder, with an estimated prevalence of 0.6 to 1.3% in the general population.1, 2However, the proportion of patients with symptomatic VWD who require treatment is rare, with a prevalence of 23 to 113 per million population, or up to 1 in 1,000 in certain clinical settings.3, 4VWD is caused by a deficiency or dysfunction of von Willebrand factor (VWF).5, 6VWF is essential for primary hemostasis as it mediates platelet adhesion to the subendothelium at sites of vascular injury.