A hereditary bleeding disorder, hemophilia results from the deficiency of specific clotting factors. Hemophilia A (classic hemophilia), which affects more than 80% of all hemophiliacs, results from a deficiency of factor VIII; hemophilia B (Christmas disease), which affects 15% of hemophiliacs, results from a deficiency of factor IX.
The severity and prognosis of bleeding disorders vary with the degree of deficiency and the site of bleeding. The overall prognosis is best in mild hemophilia, which doesn’t cause spontaneous bleeding and joint deformities.
Advances in treatment have greatly improved the prognosis, and many hemophiliacs live normal life spans. Surgical procedures can be done safely at special treatment centers for hemophiliacs under the guidance of a hematologist.
Hemophilia is caused by a deficiency of clotting factors that are genetically transmitted.
Hemophilia is the most common X-linked genetic disease, occurring in about 1.25 in 10,000 live male births. Hemophilia A is five times more common than hemophilia B. Hemophilia causes abnormal bleeding because of a specific clotting factor malfunction. After a person with hemophilia forms a platelet plug at a bleeding site, clotting factor deficiency impairs the capacity to form a stable fibrin clot.
Signs and symptoms
Hemophilia produces abnormal bleeding, which may be mild, moderate, or severe, depending on the degree of factor deficiency.
The mild form of hemophilia frequently goes undiagnosed until adulthood because the patient with a mild deficiency doesn’t bleed spontaneously or after minor trauma but has prolonged bleeding if challenged by major trauma or surgery. Postoperative bleeding continues as a slow ooze or ceases and starts again up to 8 days after surgery.
Moderate and severe hemophilia
Moderate hemophilia causes symptoms similar to those of severe hemophilia but produces only occasional spontaneous bleeding episodes.
Severe hemophilia causes spontaneous bleeding. The first sign of severe hemophilia is usually excessive bleeding after circumcision. Later, spontaneous bleeding or severe bleeding after minor trauma may produce large subcutaneous and deep intramuscular hematomas.
Bleeding into joints and muscles causes pain, swelling, extreme tenderness and, possibly, permanent deformity. Bleeding near peripheral nerves may cause peripheral neuropathies, pain, paresthesia, and muscle atrophy.
If bleeding impairs blood flow through a major vessel, it can cause ischemia and gangrene. Pharyngeal, lingual, intracardial, intracerebral, and intracranial bleeding may lead to shock and death.
A history of prolonged bleeding after trauma or surgery (including dental extractions) or of episodes of spontaneous bleeding into muscles or joints usually indicates some defect in the hemostatic mechanism.
Specific coagulation factor assays can diagnose the type and severity of hemophilia. A positive family history can also help diagnose hemophilia, but 20% of all cases have no family history.
Characteristic findings in hemophilia A include:
factor VIII assay 0% to 30% of normal
prolonged partial thromboplastin time (PTT)
normal platelet count and function, bleeding time, and prothrombin time.
Characteristics of hemophilia B include:
deficient factor IX-C
baseline coagulation results similar to those in hemophilia A, with normal factor VIII.
In hemophilia A or hemophilia B, the degree of factor deficiency determines severity:
mild hemophilia—factor levels 5% to 40% of normal
moderate hemophilia—factor levels 1% to 5% of normal
severe hemophilia—factor levels less than 1% of normal.
Hemophilia isn’t curable, but treatment can prevent crippling deformities and prolong life expectancy. Correct treatment quickly stops bleeding by increasing plasma levels of deficient clotting factors to help prevent disabling deformities that result from repeated bleeding into muscles and joints.
Treatment varies according to the type of hemophilia. Gene therapy has shown promise for both types.
In hemophilia A, cryoprecipitated antihemophilic factor (AHF), lyophilized AHF, or both, given in doses large enough to raise clotting factor levels above 25% of normal can permit normal hemostasis. Before surgery, AHF is administered to raise clotting factors to hemostatic levels. Levels are then kept within a normal range until the wound has completely healed.
In hemophilia B, administration of factor IX concentrate during bleeding episodes increases factor IX levels.
VN:F [1.9.20_1166]Introduction to Hemophilia,