Hemophilia is a genetic bleeding disorder that prevents the blood from clotting normally. The main symptom is uncontrolled, often spontaneous bleeding. Internal bleeding into the joints can result in pain, swelling and, if left untreated, can cause permanent damage. While hemophilia is almost always seen in men, von Willebrand disease is a type of hemophilia that affects women equally. It is caused by a deficient or defective blood protein known as von Willebrand factor.