Haemophilia B: Where are we now and what does the future hold?

Research has been lacking on the natural history, complications, and treatment of haemophilia B, which is less common than haemophilia A and was recognized as a distinct clinical entity in 1947. Although the two diseases share the same clinical manifestations, they differ in causative mutation, risk of inhibitor development, and patient quality of life. Frequently debated is whether haemophilia B is as clinically severe as haemophilia A, with much of the published data on overall and haemophilia-specific health outcomes suggesting that haemophilia B may have a less severe clinical phenotype. However, although fewer haemophilia B than haemophilia A patients appear to experience bleeding, bleeds are just as severe. We review distinguishing characteristics of haemophilia B and its treatment, including management strategies for neonates, therapeutic approaches for patients who develop inhibitors, pharmacokinetics of factor IX concentrates administered as replacement therapy, and potential future treatments.