Clinical manifestations of aHUS are similar to another thrombotic microangiopathy known as thrombotic thrombocytopenic purpura (TTP) which is caused by a decrease in the function of VWF-cleaving protease ADAMTS-13 (A Disintegrin And Metalloproteinase with a ThromboSpondin type 1 motif). The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.