Von Willebrand’s disease

on 9.2.09 with 0 comments

  • Quantitative or qualitative decrease in vWF (which is produced by endothelial cells and megakaryocytes; the most active forms of vWF are intermediate to large sized multimers)

  • AD, but may be AR

  • C/S variable but include spontaneous bleeding from mucus membranes, excessive bleeding from wounds, menorrhagia, and prolonged bleeding time in the presence of a normal platelet count

  • vWF causes adhesion of platelets to exposed subendothelial collagen and promotes platelet aggregation; it also acts as a cofactor in activation of factor X (when bound to factor VIII) and protects the bound factor VIII from degradation…because of this, the aPTT may be prolonged and levels of factor VIII decreased

  • Bleeding time is prolonged and PT and platelet counts are normal

  • Treatment involves replacing vWF and factor VIII through transfusion of cryoprecipitated plasma; factor VIII levels and correction of bleeding time are used to monitor adequacy

  • 2 major categories

    • Types I & III

      • Can make vWF, but release of multimers impaired

      • Type I

        • AD, 70% of cases

        • Relatively mild

      • Type III

        • AR, more severe

        • DDAVP may be helpful with cryoprecipitate therapy because it stimulates the release of vWF from endothelial cells

    • Type II

      • Can’t make vWF multimers

      • AD, accounts for 25% of cases

      • Mild to moderate bleeding

      • DDAVP may not be helpful since multimers are bad (may even be harmful due to the production of systemic platelet aggregation and resultant thrombosis)

Category: Medical Subject Notes , Pathology Notes



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