Service d'hématologie biologique, hôpital Antoine-Béclère, 157, rue de la Porte-de-Trivaux, 92140 Clamart.
Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) which pathophysiology relies on the presence, in the microcirculation, of platelet thrombi involving ultralarge multimers of von Willebrand factor (vWF), a glycoprotein essential to hemostasis. In TTP, the abnormal presence in plasma of these multimers is related to both an endothelial injury as well as to a deficiency of a specific vWF-cleaving protease, an enzyme recently identified and still incompletely characterized. This deficiency, which may be constitutional or acquired via an inhibitor, does not seem to be involved in other TMA, especially the hemolytic and uremic syndrome, and may be substituted by plasma infusion. Thus, the specific vWF-cleaving protease brings new insights in the diagnostic and therapeutic strategy of TMA.