Factor IX inhibitor

General Information

Hemophilia is a hereditary disease caused by a deficiency of one of the coagulation factors. This is due to a defect in the factor synthesizing gene.

The genes for coagulation factors 8 and 9 are present on the sex X chromosome.

Hemophilia B is an X-linked recessive disease that occurs predominantly in boys because they only have one X chromosome that they inherit from their mother. All daughters of affected boys will also carry the hemophilia gene in 100% of cases, and all sons of affected males will be healthy. 50% of sons of women carrying the abnormal gene will be affected, and 50% of daughters will be carriers.

Acquired hemophilia B is a rare autoimmune disease that develops in patients without a family history of bleeding. The cause of the disease is autoantibodies that develop against clotting factors. Before developing acquired hemophilia, such patients usually have an autoimmune disease, a malignant or infectious process, such as immunodeficiency virus, hepatitis B or C, and others.

Inhibitors of coagulation factor IX develop in patients with severe hemophilia after transfusion of factor 9. An anaphylactic reaction may also occur. The development of factor IX inhibitors in previously healthy individuals (without coagulation factor deficiency) is very rare.

Coagulation factor inhibitors (ie, circulating anticoagulants, or inactivators) are endogenous antibodies that interfere with the blood clotting process. These antibodies do not exist in plasma within normal limits. Their amount in the blood is measured by Bethesda titer units (BU). A titer of 5 Bethesda units (BU) is classified as a weak immune response, and a titer of 10 BU is considered an elevated immune response.

Factor IX inhibitors are administered in 3-5% of patients with hemophilia B in response to factor IX, prothrombin complex, or plasma transfusion. Antibodies against other clotting factors are very rare.

Inhibitors complicate bleeding episodes because they reduce sensitivity to treatment. Inhibitors should be suspected if bleeding does not stop despite coagulation factor replacement therapy.

Preparation of the patient: The study is performed on an empty stomach, against the background of discontinuation of anticoagulants

Study sample: Venous blood

Referral norms: 65-140% in adults