VWF and thrombotic thrombocytopenic purpura: Failure to remove endothelium-bound VWF allows individual multimers to self-associate to form long strands that facilitate platelet adhesion and thrombus formation, which promotes microvascular occlusion in a group of life-threatening disorders that include thrombotic thrombocytopenic purpura (TTP)2, haemolytic uraemic syndrome9 and other vascular diseases10, 11.