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Introduction: The 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. Aim: This Chinese nationwide study of HB inhibitor patients explored their risk factors for FIX inhibitor development and experience on their management. Methods: We retrospectively analysed patient characteristics, F9 genotypes, treatment strategies and outcomes of HB inhibitor patients registered to the Chinese National Registry and Patient Organization Registry. Results: Forty‐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. Conclusion: This 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. [ABSTRACT FROM AUTHOR]

Introduction: Haemophilia A (HA) is a rare X chromosome‐linked bleeding disorder resulting in missing or defective clotting factor VIII (FVIII) and causes large disease burden. Aim: As a member of World Federation of Hemophilia, China seeks to understand the current epidemiology, disease profile and treatment landscape of patients with HA through the Hemophilia Treatment Center Collaboration Network of China (HTCCNC). Methods: The HTCCNC enabled data collection on patients with HA from 166 member hospitals (2007–2019) across China. The distribution of patients across 31 divisions was summarized using a heat map. Patient demographics, disease severity and clinical and treatment information were summarized using descriptive statistics. Results: HTCCNC identified 17,779 patients with HA during 2007–2019. Patients were predominantly male (99.99%), and 28.3% had a known family history of haemophilia. Among patients with lab‐measured disease severity (N = 13,116), 6,519 had severe HA (49.7%), 4,788 had moderate HA (36.5%), and 1,809 had mild HA (13.8%). Among patients with information on the delays, delays in diagnosis and in treatment initiation were observed in 1,437 (28.8%) and 1,750 (39.2%) patients, respectively. On average, those patients had an 8.4 years gap between the first bleed and HA diagnosis and a delay of 8.6 years from the first bleed to treatment initiation. Additionally, 44.33% of patients relied solely on episodic treatments, and 16.2% received any prophylaxis treatments. Conclusions: Using data from the largest haemophilia registry in China, this study indicated that delayed diagnosis and treatment, together with low utilization of prophylaxis, are key challenges for patients with HA. [ABSTRACT FROM AUTHOR]