ADAMTS13 and thrombotic thrombocytopenic purpura: Complement involvement has also been demonstrated in thrombotic thrombocytopenic purpura (TTP) and in Shiga toxin-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS), but, in these cases, it occurs as a secondary event, triggered either by ADAMTS13-deficiency or toxin-mediated injury, respectively (5).