Multiple etiologies can lead to development of TMA, including infection with Shiga-like toxin-producing bacteria causing typical HUS (STEC-HUS), genetically determined dysregulation of the AP, which predisposes to atypical hemolytic uremic syndrome (aHUS), or A Disintegrin and Metalloproteinase with ThromboSpondin motif repeats 13 (ADAMTS13) deficiency resulting in thrombotic thrombocytopenic purpura (TTP). This evidence concerns the gene ADAMTS13 and atypical hemolytic-uremic syndrome.