Thromb Haemost 2013; 109(01): 24-33
DOI: 10.1160/TH12-05-0302
Blood Coagulation, Fibrinolysis and Cellular Haemostasis
Schattauer GmbH

Assessment of the F9 genotype-specific FIX inhibitor risks and characterisation of 10 novel severe F9 defects in the first molecular series of Argentinian patients with haemophilia B

Claudia Pamela Radic
1   Instituto de Medicina Experimental (IMEX), CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Liliana Carmen Rossetti
1   Instituto de Medicina Experimental (IMEX), CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Miguel Martín Abelleyro
1   Instituto de Medicina Experimental (IMEX), CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Miguel Candela
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Raúl Pérez Bianco
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Miguel de Tezanos Pinto
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Irene Beatriz Larripa
1   Instituto de Medicina Experimental (IMEX), CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
,
Anne Goodeve
3   Sheffield Diagnostic Genetics Service, Sheffield Children’s NHS Foundation Trust, Sheffield, UK
,
Carlos Daniel De Brasi
1   Instituto de Medicina Experimental (IMEX), CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina
2   Instituto de Investigaciones Hematológicas Mariano R Castex, Academia Nacional de Medicina, Buenos Aires, Argentina
› Author Affiliations
Financial support: This study was supported by grants from the René Barón Foundation, the Alberto J. Roemmers Foundation, the Florencio Fiorini Foundation, Novo Nordisk Argentina, the Academia Nacional de Medicina de Buenos Aires, the National Research Council (CONICET), the National Agency for Science and Technology Promotion (ANPCyT) and the Word Federation of Hemophilia.
Further Information

Publication History

Received: 05 April 2012

Accepted after major revision: 13 September 2012

Publication Date:
25 November 2017 (online)

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Summary

In haemophilia B (HB) (factor IX [FIX] deficiency), F9 genotype largely determines clinical phenotype. Aimed to characterise Argentinian families with HB, this study presents F9 genotype frequencies and their specific FIX inhibitor risk and 10 novel F9 mutations. Ninety-one DNA samples from HB patients and relatives were subjected to a new scheme: a primary screen for large deletions, a secondary screen for point mutations using conformation sensitive gel electrophoresis, DNA-sequencing and bioinformatic analysis. Our unbiased HB population (N=52) (77% with severe, 11.5% moderate and 11.5% mild HB) showed 32 missense (61.5%), including three novel mutations predicting specific structural/functional defects in silico, seven nonsense (13.5%) (one novel), five large deletions, four splice including three novel mutations affecting predicted splicing scores, three indels (two novel) and one Leiden mutation. Our comprehensive HB population included five patients with long-lasting FIX inhibitors: three nonsense (p.E35* (novel), p.R75*, p.W240*) and two entire-F9 deletions. Another patient with an indel (p.A26Rfs*14) developed transient inhibitors. A case-control analysis, based on our global prevalence of 3.05% for developing inhibitors in HB revealed that missense mutations were associated with a low risk odds ratio (OR) of 0.05 and a prevalence of 0.39%, whereas nonsense and entire-F9 deletions had significantly higher risks (OR 11.0 and 32.7) and prevalence (14.3% and 44.5%, respectively). Our cost-effective practical approach enabled identification of the causative mutation in all 55 Argentine families with HB, analysis of the molecular pathology of novel F9 defects and determination of mutation-associated FIX inhibitor risks.