Identification of Molecular Mutations Causing Haemophilia B From China: A Single-Center Experience

To identify F9 gene mutations in patients with hemophilia B registered in Nanjing Drum Tower Hospital Hemophilia Registeration Center. Methods: One stage method was used to detect APTT, PT, TT, Fg and the activities of endogenous coagultation factors. Correction testing was employed to exclud the existence of inhibitor with mixed normal plasma. Genomic DNA was extracted from blood samples of 19 unrelated haemophilia B patients and their traceable family members. All exons and their flanking sequences of the F9 gene were amplificated by PCR and subsequently, the products were purified and sequenced directly. Results: APTT was significantly prolonged for all 19 cases of hemophilia B patients, but could be corrected by mixed normal plasma. According to the serial number, FIX:C was 3.7%, 3.5%, 1.9%, 1.9%, 2.2%, 2.0%, 1.9%, 3.2%, 3.5%, 10.8%, 7.8%, 2.2%, 3.8%, 2.3%, 1.6%, 1.4%, 3.7%, 7.8% and 3.5%, respectively. Thirteen different mutations of F9 gene were identified, including C 20518 T, T 6427 C, C 6460 T, C 31008 G, C 17761 T, A 17759 G, G 30150 A, G 31093 C, T 30930 C, G 20565 A, G 30987 A, A 6473 G and C 9 G, respectively. The mutations were composed of 10 missense mutations, one nonsense mutation, one a donor splice site mutation and one promoter mutation. Among them, mutations sites nt6460, nt17761, nt20518, nt30150 and nt31008 were located in CpG islands, belonging to mutation hot-spots. Mutations including C 9 G, C 31008 G and G 31093 C were firstly reported. Conclusions: No inhibitors are detected in the plasma of all patients. The F9 mutations are heterogenous and the missense mutations are the most prevalent gene defects in Chinese HB patients.

No relevant conflicts of interest to declare.