Preview Haemophilia A and B are rare bleeding disorders caused by mutations in the genes encoding coagulation factor VIII (FVIII) and factor IX (FIX)1. The prevalence of haemophilia A is 1 in 5,000 males in the general population, while that of haemophilia B is 1 in 40,0001,2. Patients with plasma factor levels 5 IU/dL as having moderate or mild haemophilia, respectively2. Patients with mild haemophilia bleed excessively only after surgery, tooth extractions or major injuries, whereas patients with moderate haemophilia bleed even after relatively minor trauma and those with severe haemophilia bleed spontaneously or after trivial trauma. Severe haemophilia is characterised by limb- or life-threatening symptoms such as haemarthrosis, soft-tissue haematoma, retroperitoneal and intracerebral haemorrhage and post-surgical bleeds. Complications from recurrent joint bleeding and soft-tissue haematomas include severe arthropathy, muscle contractures and pseudotumours, leading to chronic pain and disability that often warrant the intervention of the orthopaedic surgeon3-5. All these complications can be effectively prevented by the regular intravenous infusion of plasma-derived or recombinant products containing the deficient coagulation factor, and this prophylactic regimen is the mainstay of modern haemophilia care. [...]