Characterization of an occult inhibitor to factor IX in a haemophilia B patient |
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| Authors: | Connie H.,Miller ,Karen H.,Orstavik Margaret W.,Hilgartner&dagger |
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| Affiliation: | Department of Medicine, Division of Hematology, Mount Sinai School of Medicine, University of Oslo;Institute of Medical Genetics, University of Oslo;Division of Pediatric Hematology/Oncology, New York Hospital–Cornell University Medical College |
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| Abstract: | Six haemophilia B patients were studied while undergoing infusion with factor IX concentrate. All were negative for factor IX antigen (IX:AG) and inhibitor to factor IX coagulant activity (IX:C). One patient showed an atypical response pattern, with prolonged survival of IX:C and IX:Ag. This patient remained under prophylactic treatment and more than 1 year later developed an inhibitor to IX:C of clinical significance. Retrospective study revealed that this patient had significantly higher levels of circulating immune complexes than other haemophilia B patients and in vivo formation of immune complexes containing IX:Ag prior to detection of his inhibitor in conventional clotting assays, suggesting long-term persistence of an occult inhibitor. The inhibitor was shown to be an IgG antibody with both kappa and lambda light chains. |
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