VWF and thrombotic thrombocytopenic purpura: The major motivation for understanding the function of the VWF‐cleaving protease came from the demonstration that its deficiency was the cause of the fatal disease thrombotic thrombocytopenic purpura (TTP) 13, 14, 15 and from the identification of its gene, designated ADAMTS1316, 17, 18, 19, 20 (Fig. 1B).