Factor VIII haplotypes in severe hemophilia A patients in India

F8 gene mutation profile in Indian hemophilia A patients: Identification of 23 novel mutations and factor VIII inhibitor risk association

'FVIII inhibitors', especially in severe hemophilia A (HA) patients, is a serious adverse effect that complicates their clinical management. Many genetic and non-genetic risk factors have been proposed for FVIII inhibitor development, diverse in different population groups. This is the first study in Indian hemophiliacs that analyzes inhibitor risk in relation to the complete F8 mutation profile, in a case-control study that included 145 Indian severe HA patients, i.e. 69 inhibitor positive (with 18 inhibitor concordant/discordant family members), and 58 inhibitor negative patients, after informed consent. While 53.54% (68/127) index cases were positive for intron 22 or intron 1 inversions, 55 causative F8 mutations were detected in the 59 inversion negative patients, of which 23 were novel mutations (in 24 patients) and 32 were reported earlier (in 35 patients). A higher incidence of mutations, in the C1 and C2 domains in inhibitor positive patients, and in the A1 domain in inhibitor negative patients was observed, though not significantly different. The study suggests that large F8 rearrangements (significantly higher in the inhibitor positive patients) pose the highest risk, while missense mutations (significantly higher in the inhibitor negative patients) pose the lowest risk of inhibitor development in Indian hemophilia A patients.

Analysis of F8 inversions as risk factors for FVIII inhibitor development in Indian severe haemophilia A patients

FVIII inhibitor development in haemophilia A (HA) patients, especially those with severe manifestations is a serious adverse effect in patients with haemophilia A, and the clinical management of these patients is very difficult as most don't respond to conventional treatment. Many genetic and non-genetic risk factors have been proposed however, these are diverse in different population groups, highlighting the importance of determining specific risk factors for each population. F8 mutations and especially inversions, which are the most common causative mutation in severe HA, have been significantly associated with inhibitor development earlier, however there is no conclusive data so far with regard to Indian haemophiliacs. This study provides novel evidence that intron 22 inversions in the F8 gene are indeed significantly associated with FVIII inhibitor development in Indian haemophiliacs. Further studies with other risk factors would enable better insights into the immune response towards FVIII in these patients, and possibly help to characterize patients at a higher risk for inhibitor development.

The Epidemiology of FVIII Inhibitors in Indian Haemophilia A Patients

A serious complication of replacement therapy in patients with bleeding disorders is the development of 'inhibitors', particularly FVIII inhibitors in haemophilia A patients. This leads to an increase in the management cost, morbidity and mortality, especially post-operatively. The mechanism of FVIII inhibitor development is quite complex and it is difficult to predict inhibitor development, but a prompt and accurate diagnosis is critical as early therapy can save lives. The aim of this study was to screen patients with bleeding disorders in India for inhibitors, and to analyse and compare the prevalence of inhibitors in different regions in India. Patient details were recorded and blood samples were collected in sodium citrate vacutainers from 1,505 patients with bleeding disorders, in different cities in India. Coagulation and inhibitor screening assays were performed, followed by the Bethesda assay in inhibitor positive samples to quantify the FVIII inhibitor titre. Out of the 1,505 samples analysed, 1,285 were Haemophilia A patients, out of which 78 (6.07 %) were positive for 'FVIII Inhibitors'. The highest incidence of FVIII Inhibitors was seen in South India (13.04 %). The highest incidence of 20.99 % was observed in Chennai, followed by Hyderabad (13.33 %), Jammu (9.90 %) and Guwahati (8.51 %), respectively, with respect to the samples analysed. The other regions showed an inhibitor incidence <8 %. The incidence of inhibitors in haemophilia A patients is different in different regions of India; this may be due to the intensity of treatment, type of product or the genetic characteristics of these patients.