Familial acquired thrombotic thrombocytopenic purpura: ADAMTS13 inhibitory autoantibodies in identical twins

(TTP) either occurs in a congenital form caused by ADAMTS13 gene mutations or it is acquired and most often due to ADAMTS13 inhibitory autoantibodies. In congenital TTP siblings are often af-fected, while acquired TTP occurs spo-radically and familial clustering has not been described so far. We report identical twin sisters suffering from acquired TTP due to immunoglobulin G (IgG) autoanti-bodies inactivating ADAMTS13, suggest-ing an important role of hitherto unidenti-fied genetic determinants of ADAMTS13 inhibitor formation. These cases also demonstrate that familial clustering is not sufficient for unambiguously diagnosing hereditary ADAMTS13 deficiency and con-genital TTP. (Blood. 2004;103:4195-4197) © 2004 by The American Society of Hematolog