A number of rare bleeding disorders exist. Clotting factors are proteins in the blood that control bleeding. If any of the clotting factors are missing or not working properly, the normal steps leading to coagulation are blocked. When this happens, the blood clot does not form and the bleeding continues for longer than it should. A deficiency of any one of these clotting factors can cause a rare bleeding disorder. Here is a brief overview of rare clotting factor deficiencies.