VWF and thrombotic microangiopathy: Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) resulting from hereditary or immune-mediated deficiency of the enzyme ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motifs, member 13) activity, leading to impaired cleavage of high-molecular-weight von Willebrand factor (HMW-VWF) multimers, with clinical manifestations of severe thrombocytopenia, microangiopathic hemolysis, and thrombosis-induced multiorgan functional impairment (1).