Von Willebrand Disease

A genetic blood disease where there is a malfunction in the Von Willebrand clotting factor, a factor that works with factor VIII, is missing or does not function normally causing blood not to clot properly. It is the most common hereditary coagulation abnormality in people. It is characterized by a tendency to hemorrhage, and caused by a defect in blood platelet activity.

Clotting process:

  • Damaged cells display a surface protein called tissue factor (TF)
  • Tissue factor binds to activated Factor 7.
  • The TF-7 heterodimer is a protease with two substrates:
    • Factor 10 and
    • Factor 9
  • Factor 10 binds and activates Factor 5. This heterodimer is called prothrombinase because it is a protease that converts prothrombin (also known as Factor II) to thrombin.
  • Thrombin has several different activities. Two of them are:
    • proteolytic cleavage of fibrinogen (aka “Factor I”) to form:
      • soluble molecules of fibrin and a collection of small
      • fibrinopeptides
    • activation of Factor 13 which forms covalent bonds between the soluble fibrin molecules converting them into an insoluble meshwork — the clot.
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    Blood Clotting. Retrieved September 15, 2009 from http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Clotting.html

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