Importantly, inhibitory autoantibodies against the von Willebrand factor–cleaving protease (ADAMTS13 inhibitor) were negative in both cases, suggesting that the observed TMA was unlikely related to acquired thrombotic thrombocytopenic purpura (TTP) mediated by severe ADAMTS13 deficiency. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.