ADAMTS13 and hemolytic-uremic syndrome: However, at present, the differential diagnosis of aHUS from other thrombotic microangiopathies (TMA) is essentially made after ruling out severe ADAMTS13 deficiency (thrombotic thrombocytopenic purpura, TTP), infection with Shiga-like toxin producing bacteria (STEC-HUS), or coexisting conditions assumed to be the etiologic disease factor (secondary HUS) (5).