What is the pathophysiology of thrombotic thrombocytopenic purpura (TTP)?

Updated: Feb 18, 2019
  • Author: Theodore Wun, MD, FACP; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Answer

TTP can affect any organ system, but involvement of the peripheral blood, the central nervous system, and the kidneys causes the clinical manifestations. The classic histologic lesion is one of bland thrombi in the microvasculature of affected organs. These thrombi consist predominantly of platelets with little fibrin and red cells compared with thrombi that occur secondary to intravascular coagulation. The ultimate cause of TTP is unknown; however, research has uncovered some clues about the pathophysiology.

Patients with TTP have unusually large multimers of von Willebrand factor (vWF) in their plasma, and they lack a plasma protease that is responsible for the breakdown of these ultralarge vWF multimers. In the congenital form of TTP, mutations in the gene encoding this protease have been described. In the more common sporadic form, an antibody inhibitor can be isolated in most patients. This protease has been isolated and cloned and is designated ADAMTS13 (A Disintegrinlike And Metalloprotease with ThromboSpondin type 1 motif 13). [7] The activity of this protease is normal in most patients with classic HUS, suggesting differing pathogenesis of these closely related entities. [8]


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