ADAMTS13 and thrombotic thrombocytopenic purpura: They are classified in three different disease entities according to the underlying pathophysiology: thrombotic thrombocytopenic purpura (TTP), caused by severe deficiency of the von-Willebrand Factor-cleaving protease called ADAMTS13 [5], hemolytic uremic syndrome (HUS), caused by Shiga toxin-producing Escherichia coli (STEC-HUS) and atypical HUS (aHUS) [6].