VWF and thrombotic thrombocytopenic purpura: Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic disease characterized by a severe deficiency in the activity of a specific von Willebrand factor (VWF)-cleaving protease, a disintegrin-like metalloproteinase with thrombospondin type 1 motif 13 (ADAMTS-13) [1].