Congenital haemophilia A (HA) and B (HB) are bleeding disorders characterised by a deficiency of blood clotting factor VIII (FVIII) or factor IX (FIX), respectively.1The type of FVIII/IX mutation present is a major determinant of severity and bleeding tendency.1Severe cases present with bleeding and joint bleeds from early childhood, which, without appropriate treatment and prevention, can result in irreversible joint damage and chronic arthropathy.2 This evidence concerns the gene F9 and hemophilia A.