VWF and thrombotic thrombocytopenic purpura: Moake et al.1 reported in 1982 the first evidence that the pathogenesis of the main form of microangiopathy, that is Thrombotic Thrombocytopenic Purpura (TTP), arises from a defect in proteolytic processing of von Willebrand factor (VWF), a multimeric glycoprotein with very high molecular weight that plays an essential role in platelet-dependent hemostasis.