title: Prevalence, causes, and characterization of factor XI inhibitors in patients with inherited factor XI deficiency.
abstract: Factor XI deficiency, an injury-related bleeding disorder, is rare worldwide but common in Jews in whom 2 mutations, Glu117Stop (type II) and Phe283Leu (type III), prevail. Mean factor XI activities in homozygotes for Glu117Stop and for Phe283Leu are 1 and 10 U/dL, respectively. Inhibitors to factor XI in patients with severe factor XI deficiency have been reported in a small number of instances. This study was undertaken to determine the prevalence of acquired inhibitors against factor XI in patients with severe factor XI deficiency, discern whether these inhibitors are related to specific mutations, and characterize their activity. Clinical information was obtained from unrelated patients with severe factor XI deficiency, and blood was analyzed for factor XI activity, inhibitor to factor XI, and causative mutations. Immunoglobulin G purified from patients with an inhibitory activity was tested for binding to factor XI, effects on activation of factor XI by factor XIIa and thrombin, and activation of factor IX by exogenous factor XIa. Of 118 Israeli patients, 7 had an inhibitor; all belonged to a subgroup of 21 homozygotes for Glu117Stop who had a history of plasma replacement therapy. Three additional patients with inhibitors from the United Kingdom and the United States also had this genotype and were exposed to plasma. The inhibitors affected factor XI activation by thrombin or factor XIIa, and activation of factor IX by factor XIa. The results imply that patients with a very low factor XI level are susceptible to development of an inhibitor following plasma replacement.
authors.affiliation: Thrombosis and Hemostasis Research Institute, Tissue Typing Laboratory, Sheba Medical Center, Tel Hashomer, Israel.
authors.forename: Ophira
authors.initials: O
authors.lastname: Salomon
authors.forename: Ariella
authors.initials: A
authors.lastname: Zivelin
authors.forename: Tami
authors.initials: T
authors.lastname: Livnat
authors.forename: Rima
authors.initials: R
authors.lastname: Dardik
authors.forename: Ron
authors.initials: R
authors.lastname: Loewenthal
authors.forename: Ophelia
authors.initials: O
authors.lastname: Avishai
authors.forename: David M
authors.initials: DM
authors.lastname: Steinberg
authors.forename: Michael H
authors.initials: MH
authors.lastname: Rosove
authors.forename: Niamh
authors.initials: N
authors.lastname: O'Connell
authors.forename: Christine A
authors.initials: CA
authors.lastname: Lee
authors.forename: Uri
authors.initials: U
authors.lastname: Seligsohn
mesh_terms: D000368:Aged; D001323:Autoantibodies / Q000097:blood; D005164:Factor IX / Q000378:metabolism; D015942:Factor VIIa / Q000494:pharmacology; D005172:Factor XI / Q000276:immunology / Q000378:metabolism; D005173:Factor XI Deficiency / Q000453:epidemiology* / Q000209:etiology* / Q000235:genetics / Q000276:immunology; D015956:Factor XIIa / Q000494:pharmacology; D015945:Factor XIa / Q000494:pharmacology; D005260:Female; D005838:Genotype; D000949:Histocompatibility Antigens Class II / Q000235:genetics; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007557:Israel; D007585:Jews; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010314:Partial Thromboplastin Time; D010949:Plasma; D011994:Recombinant Proteins / Q000494:pharmacology; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology; D006113:United Kingdom; D014481:United States
chemical_list: D001323:Autoantibodies; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D005164:Factor IX; D005172:Factor XI; D015942:Factor VIIa; D015945:Factor XIa; D015956:Factor XIIa; D013917:Thrombin