Hemophilia is the most common hereditary clotting disorder (see also Overview of Blood Clotting Disorders). Hemophilia involves an inherited deficiency of certain clotting factors (proteins that help the blood clot, stopping bleeding). In hemophilia A, clotting factor VIII is deficient and in hemophilia B, factor IX is deficient. However, rarely people have an inherited deficiency of another clotting factor. Examples include a deficiency of factor II, V, VII, X, XI or XIII. Most of these disorders are inherited in an autosomal recessive fashion. In other words, the person needs to receive two copies of the abnormal gene, one from each parent.
People with deficiencies of these clotting factors bruise easily and may have bleeding that is hard to stop (see also Bruising and Bleeding). Bleeding that is difficult to control after injury or surgery in a person who does not have hemophilia may indicate that a person has an uncommon clotting disorder. Doctors measure the levels of clotting factors in a blood sample in people who experience bruising or bleeding that is difficult to control.
Treatment depends on the specific factor that is deficient but usually includes replacing the deficient clotting factor.
Deficiency of factor XI is the most common of the rare inherited clotting disorders. About half of cases of factor XI deficiency occur among people of Eastern European Jewish ancestry. Factor XI deficiency affects both males and females and may cause bleeding after injury or surgery (often dental surgery). Spontaneous bleeding episodes are usually less frequent and milder than in hemophilia A or B.
Alpha 2-antiplasmin blocks the activity of plasmin, which is a substance in the blood that helps dissolve blood clots. In a rare hereditary disorder, the level of alpha 2-antiplasmin is severely low, and excessive bleeding can occur. Doctors can measure the level of alpha 2-antiplasmin in people who have excessive bleeding and have had other causes excluded. Aminocaproic acid or tranexamic acid is used to control or prevent bleeding.