Von Willebrand disorder (vWD) is the most common inherited bleeding ailment. People with vWD have defects in or reduced levels of von Willebrand factor (vWF), an adhesive plasma protein essential for clotting the blood. It is not usually fatal, although it is much more severe if one inherits the gene from both parents.
Von Willebrand's disease affects 1 in 100 people, causing frequent nosebleeds, bleeding gums and excessive menstrual flow. The level of von Willebrand factor increases in the blood with age, so children are more prone to the disease than are adults.