Intron 22 and intron 1 inversions of the F8 gene as predisposing risk factors for inhibitor development in Indian severe haemophilia a patients

Abstract

Inversions in the F8 gene (in intron 22 and intron 1) are the causative mutations in around 50 % of severe haemophilia A patients and are thought to be important genetic risk factors for the development of 'FVIII inhibitors' in certain populations. The present study was undertaken to study the association between these F8 inversions and inhibitor development, and the results suggest that intron 22 inversions are an important risk factor for FVIII inhibitor development in Indian severe haemophilia A patients. Introduction: Development of 'FVIII Inhibitors' in congenital haemophilia A patients is a serious complication of FVIII replacement therapy, and influenced by various genetic and non-genetic risk factors. Earlier studies in Indian haemophilia A patients, have shown IL10 and TNFA rs1799724 promoter polymorphisms (but not FVIII haplotypes), to be significantly associated with inhibitor development. Our aim was to analyse the association of inversions in introns 22 and 1 in the F8 gene with inhibitor development in Indian severe haemophilia A patients. Materials and Methods: 150 Indian severe hemophilia A patients, i.e. 60 consecutive inhibitor positive, 20 concordant/discordant family members, and 70 consecutive inhibitor negative patients (>10 years, >10 treatment product exposures) were included in the study after informed consent. Intron 22 Inversion was analysed by the modified I-PCR (Rossetti et al. 2005), and Intron 1 Inversion was analysed by the method described by Bagnall et al. (2002). Results were analysed for statistical significance by Fisher's exact test. Results: Intron 22 inversions were observed in 50 % inhibitor positive and 28.57 % inhibitor negative patients. Intron 1 inversions were observed in 3.33 % inhibitor positive and 5.71 % inhibitor negative patients Conclusion: Intron 22 Inversions were significantly higher in the inhibitor positive HA patients (P: 0.0184, OR: 2.500, 95 % CI: 1.211-5.161, Fisher's exact test), and among the inhibitor concordant family members, suggesting that intron 22 inversions are an important risk factor for inhibitor development. Intron 1 inversions in the two groups were not significantly different. Association studies with other risk factors could provide further insights into the FVIII immune response.