ADAMTS13 and thrombotic thrombocytopenic purpura: All these observations raise the question of whether malignancy-associated MAHA that is unresponsive to plasmapheresis is a form of TTP/HUS or rather is a completely different disease entity and although some reduction in ADAMTS13 metalloproteinase activity has been reported in cancer patients with hemolysis, this can also be the case in other clinical settings [37].