Von Willebrand’s disease

• 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