VWF and thrombotic thrombocytopenic purpura: Under pathophysiological states, such as thrombotic thrombocytopenic purpura (TTP), a severe deficiency in availability or activity of ADAMTS13 (<10%) results in accumulation of pro-thrombotic VWF multimer forms leading to the formation of microvascular platelet-rich thrombi, thrombocytopenia, secondary micro-hemorrhages, and peripheral blood schistocytes (14, 18).