ADAMTS13 and thrombotic thrombocytopenic purpura: The current classification includes thrombotic thrombocytopenic purpura, due to either immune or inherited deficiency in a disintegrin and metalloprotease with thrombospondin type I motif, member 13 (ADAMTS13); Shiga toxin–producing E. coli–associated HUS; secondary TMA; and primary aHUS/complement-mediated TMA (hereafter referred to as aHUS), which remains a clinical diagnosis by exclusion of other aetiologies.