If blood clots slowly or not at all, a person is at great risk for blood loss from the smallest injury. The two most common clotting disorders are hemophilia and von Willebrand disease. Hemophilia affects mostly males and is caused by a deficiency in a specific clotting factor. Von Willebrand disease is due to a deficiency in a plasma protein that interacts with specific clotting proteins. In both diseases, the severity of the condition depends on how much of the specific protein is produced.