Hemophilia

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  1. Most common bleeding disorder due to hereditary clotting factor deficiencies
  2. Two forms:
    1. hemophilia A due to factor 8 deficiency
    2. hemophilia B due to factor 9 deficiency
  3. Both transmitted on the X chromosome and so only affects males; both have the same clinical manifestations and screening test abnormalities
  4. Screening tests:
    1. prolonged PTT, normal bleeding time and normal PT
    2. 15% of patients with hemophilia A develop factor 8 antibodies that act as anticoagulants inhibiting the coagulant activity of further factor 8 administered
  5. treatment: FFP has both factor 8 and 9 but not in sufficient quantities thus cryoprecipitate (vW factor, factor 8 and fibrinogen) and factor 8 concentrate have been created for hemophilia A (DDAVP will also raise the factor 8 level slightly); for hemophilia B use FFP or prothrombin concentrate which contains factor 9 and vitamin K dependent clotting factors
    1. Patients who develop antibodies directed against replacement therapy can be treated with recombinant activated factor VII (rFVIIa)
    2. Alternative treatments: desmopressine (DDAVP), antifibrinolytic treatment ( tranexamic acid and aminocaproic acid), gene therapy
  6. vonWillebrand’s disease
    1. autosomal dominant bleeding disorder resulting from a quantitative or qualitative abnormality of vW factor, a plasma protein secreted by endothelial cells
    2. vW factor is required for platelets to adhere to collagen sites where vessels are injured and is also required for complexing with factor 8 (NOTE: there are 2 hereditary disorders that may cause factor 8 deficiency – hemophilia A and vW disease)
    3. diagnosis: decreased vW factor with normal factor 8 and ability of plasma to support agglutination of normal platelets by ristocetin; PT is normal, PTT is prolonged and platelets don’t aggregate; bleeding time is off the wall
    4. treatment: cryoprecipitate, desmopressin (synthetic analog of vasopressin that stimulates release of vW from endothelial cells)
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