Ticlopidine-Associated Thrombotic Thrombocytopenic Purpura

TO THE EDITOR: Bennett and colleagues [1] present a comprehensive review of currently identified cases of thrombotic thrombocytopenic purpura (TTP) associated with use of ticlopidine. Given the high case-fatality rate of TTP and the increasing use of ticlopidine, their description of this possible association is welcome and important. However, as with any case-series, the absence of a denominator (patient-years of exposure) makes assessment of the strength of this association difficult. In addition, as the authors note, an antiplatelet agent such as ticlopidine seems an unlikely culprit to cause a disease characterized by intravascular platelet thrombi. In fact, we have previously presented preliminary data on three patients with severe relapsing TTP whose disease went into sustained remission after treatment with ticlopidine [2]. This therapeutic trial was based on successful previous experience in Italy [3]. Given these seeming contradictions in both mechanism and effect between ticlopidine and TTP, we believe that their association may prove to be more complex than Bennett and colleagues describe.