ADAMTS13 and thrombotic thrombocytopenic purpura: TTP and HUS are specific types of TMA which clinically present with a predominance of neurological and renal end-organ injury respectively, but they are specifically defined further: TTP is specifically caused and defined by deficient ADAMTS-13 activity testing (<10%), and HUS as either infection associated or complement mediated, and defined by testing for the infectious cause (or shiga-like toxin) by stool culture/PCR, or by complement mutational analysis.