Von Willebrand Disease (vWD) is a rare bleeding disorder caused by a genetic defect. It affects about 3.2 million people in the United States, making it the most common bleeding disorder. People with vWD cannot form a suitable clot because there is an insufficient amount of von Willebrand factor in their blood, or it does not work properly. The condition is named after Finnish physician Erik von Willebrand, who first described it in the 1920s. According to the CDC, 1 in every 100 people have vWD. Women are often more likely to notice the symptoms due to heavy or abnormal menstrual bleeding and bleeding after giving birth. For more information, visit https://www.cdc.gov/ncbddd/vwd/facts.html.