Hemophilia is a genetic disorder that affects blood clotting. The two most common forms are hemophilia A and hemophilia B. Though the cause is different, the main effect is the same: people with hemophilia bleed for longer than normal. Hemophilia A and B are caused by changes in two different genes. For hemophilia A, the affected gene is F8. For hemophilia B it is F9. Both genes are on the X chromosome. The F8 gene codes for a protein called coagulation factor VIII (eight). F9 codes for the protein coagulation factor IX (nine).
Diagnosis includes screening tests and clotting factor tests. Screening tests are blood tests that show if the blood is clotting properly. Clotting factor tests, also called factor assays, determine the clotting activity of factors VIII and IX in the blood. Factors VIII and IX are proteins in the blood that help form clots and stop bleeding.
Genetic testing is the next step in providing answers. The type of testing will depend on the family and/or patient’s needs and concerns. Family members who currently have hemophilia A are tested first and then any potential carriers.
