Thrombotic Thrombocytopenic Purpura Associated With Ticlopidine in the Setting of Coronary Artery Stents and Stroke Prevention

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Abstract
THROMBOTIC thrombocytopenic purpura (TTP) is a life-threatening, multisystem disease characterized by thrombocytopenia, microangiopathic hemolytic anemia, neurologic changes, renal failure, and fever.1 The cause of acute TTP appears to be related to transient immune dysregulation and selective antigenic targeting of a metalloprotease that degrades large multimers of factor VIIIR.2,3 Ultralarge factor VIIIR multimers increase platelet adhesiveness in vitro and may be one of the platelet-aggregating agents responsible for the platelet microthrombi that characterize TTP in vivo.4 An IgG autoantibody against components of the enzyme may account for a lack of metalloprotease activity in patients with TTP. While the reasons for transient immune dysregulation and for the selective antigenic targeting of the protease are unknown, the time course of 2 to 4 weeks following certain drug exposures is consistent with an autoimmune mechanism for some cases of TTP.