– A hereditary bleeding disorder characterized by impaired coagulability of the blood.
Causes and Incidence
Hemophilia is caused by a deficiency of blood clotting factors VIII, IX, or XI, which are carried on genes on the X chromosome. Sons of men who are hemophiliacs are normal, whereas daughters are obligatory carriers. Sons of women who are carriers have a 50% chance of being hemophilic, and daughters have a 50% chance of being a carrier. Hemophilia is the most common X-linked genetic disease; it occurs in 1.25 of every 10,000 live male births in the United States.
Hemophilia A (absent factor VIII), hemophilia B (absent factor IX), and hemophilia C (absent factor XI) are the most common types. The absence of the clotting factor interferes with the intrinsic phase of the coagulation process and inhibits the formation of prothrombin activator; this interferes with the rate at which thrombin is formed from prothrombin, slowing clot formation.
The primary presenting sign is excessive, poorly controlled bleeding. The rate of bleeding depends on the amount of factor activity and the severity of the injury that caused the bleeding. A factor activity level below 1% can cause spontaneous bleeding or severe bleeding from even minor trauma. When the factor activity level is over 5%, bleeding is usually due to trauma and is more easily controlled. The bleeding may be superficial, may involve subcutaneous and muscle tissue, or may entail deep bleeding into joints and organ systems.
Joint and other musculoskeletal deformities, airway compression, pericardial tamponade, increased intracranial pressure, hemorrhagic shock, and death can result from uncontrolled or repeated bleeding. Note: Many hemophiliacs who received plasma in the early 1980s are infected with HIV. The virus was transmitted through plasma transfusions from blood banks that had contaminated blood and blood products. This occurred before reliable test measures were devised for detecting HIV in blood products and for eliminating them from the blood supply.
Laboratory tests reveal a normal prothrombin time, a prolonged partial thromboplastin time, and a normal bleeding time (platelet function). Assays are used to determine the factor affected and the level of factor activity. Genetic testing is performed to identify carriers.
None; extreme care must be exercised when these individuals need surgery for other conditions.
Aspirin use and intramuscular injections should be avoided because they may precipitate bleeding; inoculation against hepatitis B is important Plasma replacement of deficient factor as prophylaxis or to stop bleeding episode; use of immunosuppressives, plasmapheresis, prothrombin complexes, or synthetic DDAVP to treat development of antibody inhibitors against a specific factor; safety precautions in activities of daily living to prevent injury; dental maintenance to prevent need for dental surgery or tooth pulling; education of patient and family about disease process; counseling for adaptation to chronic disease.