title: Insights into abnormal hemostasis in the Quebec platelet disorder from analyses of clot lysis.
abstract: BACKGROUND
  The Quebec platelet disorder (QPD) is inherited and characterized by delayed-onset bleeding following hemostatic challenge. Other characteristics include increased expression and storage of active urokinase-type plasminogen activator (u-PA) in platelets in the setting of normal to increased u-PA in plasma. There is also consumption of platelet plasminogen activator inhibitor-1 and increased generation of plasmin in platelets accompanied by proteolysis of stored alpha-granule proteins, including Factor V.
  
  
  OBJECTIVE
  Although fibrinolysis has been proposed to contribute to QPD bleeding, the effects of QPD blood and platelets on clot lysis have not been evaluated. We used thromboelastography (TEG), biochemical evaluations of whole blood clot lysis, assessments of clot ultrastructure, and perfusion of blood over preformed fibrin to gain insights into the disturbed hemostasis in the QPD.
  
  
  RESULTS
  Thromboelastography was not sensitive to the increased u-PA in QPD blood. However, there was abnormal plasmin generation in QPD whole blood clots, generated at low shear, with biochemical evidence of increased fibrinolysis. The incorporation of QPD platelets into a forming clot led to progressive disruption of fibrin and platelet aggregates unless drugs were added to inhibit plasmin. In whole blood perfusion studies, QPD platelets showed normal adherence to fibrin, but their adhesion was followed by accelerated fibrinolysis.
  
  
  CONCLUSIONS
  The QPD is associated with "gain-of-function" abnormalities that increase the lysis of forming or preformed clots. These findings suggest accelerated fibrinolysis is an important contributor to QPD bleeding.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Diamandis
authors.forename: F
authors.initials: F
authors.lastname: Adam
authors.forename: W H A
authors.initials: WH
authors.lastname: Kahr
authors.forename: P
authors.initials: P
authors.lastname: Wang
authors.forename: K A
authors.initials: KA
authors.lastname: Chorneyko
authors.forename: A L
authors.initials: AL
authors.lastname: Arsenault
authors.forename: G E
authors.initials: GE
authors.lastname: Rivard
authors.forename: C P M
authors.initials: CP
authors.lastname: Hayward
mesh_terms: D001791:Blood Platelet Disorders / Q000503:physiopathology*; D001792:Blood Platelets / Q000473:pathology*; D002448:Cell Adhesion; D006801:Humans; D008854:Microscopy, Electron; D011792:Quebec