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

RADIC, CLAUDIA; ROSSETTI, LILIANA; ABELLEYRO, MIGUEL; CANDELA, MIGUEL; PEREZ BIANCO, RAUL; TEZANOS PINTO, MIGUEL; LARRIPA, IRENE; GOODEVE, ANNE

THROMBOSIS AND HAEMOSTASIS

SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN

Lugar: Stuttgart ; Año: 2012

0340-6245

ABSTRACT In Haemophilia B (HB) (factor IX (FIX) deficiency), F9 genotype largely determines clinical phenotype. Aimed to characterise Argentine families with HB, this study presents F9 genotype frequencies and their specific FIX inhibitor risk and 10 novel F9 mutations. Ninetyone 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, DNAsequencing 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 disturbances defects in silico, 7 nonsense (13.5%)(one novel), 5 large deletions, 4 splice including three novel mutations affecting predicted splicing scores, 3 indels (two novel) and one Leiden mutation. Our comprehensive HB population included five patients with longlasting FIX inhibitors: three nonsense (p.E35* (novel), p.R75*, p.W240*) and two entireF9 deletions. A further patient with an indel (p.A26Rfs*14) developed transient inhibitors. A casecontrol 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 entireF9 deletions had significantly higher risks (OR 11.0 and 32.7) and prevalence (14.3% and 44.5%, respectively). Our costeffective 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 mutationassociated FIX inhibitor risks