VWF and thrombotic thrombocytopenic purpura: TMAs such as thrombotic thrombocytopenic purpura, hemolytic uremic syndrome (HUS) and pre-eclampsia are characterized by widespread endothelial injury and expression of thrombogenic stimuli such as von Willebrand factor (vWF), due to the release of endotheliotropic toxins (characteristic of typical HUS), impaired inhibition of the complement system (atypical HUS) or other noncharacterized stimuli, possibly in the setting of jeopardized ADAMTS-13 activity (thrombotic thrombocytopenic purpura) [5].