title: Incidence of factor IX inhibitor development in severe haemophilia B patients treated with only one brand of high purity plasma derived factor IX concentrate.
abstract: Fifteen previously untreated patients (Pups) with severe haemophilia B (factor IX activity < or = 2 U/dl) only treated with one brand of plasma-derived high purity factor IX concentrate (FIX LFB) were studied. Age at first injection varied from 1 to 137 months and follow-up since this first injection from 21 to 86 months (median: 35). Cumulative exposure days (CED) were from 4 to over 100 (median: 26). Among these 15 Pups only one developed an inhibitor. Mutation analysis performed in all patients showed total gene deletion in the patient with inhibitor, partial gene deletion in another one, and missense mutations in 9 families. Mutation was not found in one patient. Actually, according to the data already published, only two patients were at high risk for inhibitor development in our population. Our study, although rather small, confirms the previously reported low incidence of inhibitors in haemophilia B. Large studies on incidence of FIX inhibitors are indeed difficult to perform, due to both the overall small number of severe haemophilia B patients and the low incidence of FIX inhibitors. Consequently, the impact of bias, such as prevalence of different types of gene defects in a given population, is major. Therefore, any study, dealing with incidence of FIX inhibitors in severe haemophilia B should report, for each patient, the type of gene defect.
authors.affiliation: Haemophilia Centre of ETS-Lille, France.
authors.forename: A
authors.initials: A
authors.lastname: Parquet
authors.forename: Y
authors.initials: Y
authors.lastname: Laurian
authors.forename: C
authors.initials: C
authors.lastname: Rothschild
authors.forename: R
authors.initials: R
authors.lastname: Navarro
authors.forename: C
authors.initials: C
authors.lastname: Guérois
authors.forename: V
authors.initials: V
authors.lastname: Gay
authors.forename: A
authors.initials: A
authors.lastname: Durin
authors.forename: J
authors.initials: J
authors.lastname: Peynet
authors.forename: Y
authors.initials: Y
authors.lastname: Sultan
mesh_terms: D000906:Antibodies / Q000097:blood / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D005164:Factor IX / Q000009:adverse effects / Q000276:immunology* / Q000627:therapeutic use*; D002836:Hemophilia B / Q000097:blood / Q000188:drug therapy* / Q000276:immunology*; D006801:Humans; D015994:Incidence; D007223:Infant
chemical_list: D000906:Antibodies; D005164:Factor IX