The prevalence of factor VIII inhibitors and genetic aspects of inhibitor development in Chinese patients with haemophilia A.

The prevalence of inhibitors in Chinese haemophiliacs has not yet been reported. The aim of this study was to identify the prevalence of factor VIII (FVIII) inhibitors among haemophiliacs who are treated only with plasma-derived FVIII (pdFVIII), cryoprecipitate or fresh frozen plasma (FFP), and tried to explore the relationship between the generation of inhibitors and particular FVIII deficiency genotypes. Clinical information and blood samples of 1435 patients with haemophilia A (HA) were collected by six haemophilia centres in China. The Nijmegen modification of the Bethesda assay was used to detect inhibitors. Multiplex PCR, long-range PCR and direct sequencing were performed for genotyping. The overall prevalence of inhibitors in Chinese HA patients was 3.9% and the prevalence of severe haemophiliacs was 4.3%; 18 of the 56 patients with inhibitors had high titres. A total of 38 different mutations were identified in the 55 patients with inhibitors, including 15 intron 22 and 3 intron 1 inversions, seven large deletions, 14 small deletion/insertions, seven nonsense mutations, one splice site mutations and eight missense mutations. Of 38 mutations, 28 were novel. Patients with large deletions and nonsense mutations were prone to have high titre inhibitors, with incidence rates of 57.1% (4/7) and 42.9% (3/7), respectively. In conclusion, the prevalence of inhibitors in Chinese HA patients is much lower than that reported for other ethnic groups and the large deletion and nonsense mutations are high risk factors for high titre inhibitor development.