Factor IX inhibitors in haemophilia B: A report of National Haemophilia Registry in China

• DOI: 10.1111/hae.14665
• Publication Date: 2022-09-27T04:14:06Z
• Authors: Xueqing Dou; Wenhui Zhang; Man‐Chiu Poon; Xinsheng Zhang; Runhui Wu; Xiaoqin Feng; Linhua Yang; Peng Cheng; Shu Chen; Ying Wang; Hu Zhou; Meijuan Huang; Yanping Song; Chenghao Jin; Donglei Zhang; Lingling Chen; Wei Liu; Lei Zhang; Feng Xue; Renchi Yang
• Keywords: China; Adolescent; Hemophilia A; Hemophilia B; 3. Good health; Factor IX; 03 medical and health sciences; 0302 clinical medicine; Child, Preschool; Immune Tolerance; Humans; Child; Retrospective Studies

AbstractIntroductionThe development of inhibitors against factor FIX (FIX) is the most serious complication of FIX replacement therapy in haemophilia B (HB) patients. Currently, only few cohorts of HB inhibitor patients have been reported worldwide.AimThis Chinese nationwide study of HB inhibitor patients explored their risk factors for FIX inhibitor development and experience on their management.MethodsWe retrospectively analysed patient characteristics, F9 genotypes, treatment strategies and outcomes of HB inhibitor patients registered to the Chinese National Registry and Patient Organization Registry.ResultsForty‐four unique HB inhibitor patients were identified in 4485 unique HB patients registered by year 2021 to the two Registries. Inhibitor diagnosis were usually delayed and the low prevalence (.98%) may suggest some inhibitor patients were not identified. Their median age at inhibitor diagnosis was 7.5 (IQR, 3.0–14.8) years. Most patients (95.5%) had high‐titre inhibitors. Allergic/Anaphylactic reactions occurred in 59.1% patients. Large deletions and nonsense mutations were the most common F9 mutation types in our FIX inhibitor patients. Patients with large F9 gene deletions were more likely to develop inhibitors (p = .0002), while those with missense mutations had a low risk (p < .0001). Thirteen (29.5%) patients received immune tolerance induction (ITI) therapy using low‐dose prothrombin complex concentrate regimens. Twelve completed ITI with three (25.0%) achieving success. Nephrotic syndrome developed in two (16.7%) patients during ITI.ConclusionThis study reports the largest Chinese cohort of HB inhibitor patients. Large deletions were most significantly associated with inhibitor development. Low‐dose ITI might be feasible for FIX inhibitor eradication.