ADAMTS13 and thrombotic thrombocytopenic purpura: The pathogenesis of TTP includes the decreased activity of plasma metalloproteinase ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), which is an important enzyme involved in the cleavage of von Willebrand factor (VWF) multimers [4].