Haemophilia or hemophilia is the name of any of several hereditary genetic illnesses that impair the body's ability to control bleeding. Genetic deficiencies (or, very rarely, an autoimmune disorder) cause lowered plasma clotting factor activity so as to compromise blood-clotting; when a blood vessel is injured, a scab will not form and the vessel can continue to bleed excessively for a very long period of time. The bleeding can be external, if the skin is broken by a scrape, cut or abrasion, or it can be internal, into muscles, joints or hollow organs. It might therefore present visibly as skin bruises, or subtly as melena, hematuria, or bleeding in the brain-.