To the Editor: Thrombotic thrombocytopenic purpura (TTP) is a specific form of thrombotic microangiopathy (TMA) characterized by thrombocytopenia, erythrocyte fragmentation, and widespread microvascular thrombi responsible for multi-organ failure of variable severity [1]. Surprisingly, while a profound thrombocytopenia is a typical feature of the disease, severe hemorrhage is a rare cause of mortality. Nevertheless, in case of severe bleeding or when an invasive procedure is needed (i.e., catheter insertion, spinal puncture), platelets transfusion may be required, although sudden clinical deteriorations and fatalities suggestive of a worsening of TTP within few hours after a platelet transfusion were reported [2,3]. To date, controversies remain on the effect of platelet transfusions during TTP [4–6]. In light of the uncertain risk of platelet transfusions in TTP and the lack of recently published data, we retrospectively reviewed admission data of all TTP patients with a severe acquired ADAMTS13 deficiency (\textless10% of activity in normal plasma) enrolled in the French TMA Reference Centre registry, in order to better assess the risk of platelet transfusions at the acute phase of TTP. ...Read less <