Haemophilia B

Haemophilia B is a blood clotting disorder causing easy bruising and bleeding due to an inherited mutation of the gene for factor IX, and resulting in a deficiency of factor IX. It is less common than factor VIII deficiency (haemophilia A). Haemophilia B is a blood clotting disorder causing easy bruising and bleeding due to an inherited mutation of the gene for factor IX, and resulting in a deficiency of factor IX. It is less common than factor VIII deficiency (haemophilia A). Haemophilia B was first recognized as a distinct disease entity in 1952. It is also known by the eponym Christmas disease, named after Stephen Christmas, the first patient described with haemophilia B. In addition, the first report of its identification was published in the Christmas edition of the British Medical Journal. Symptoms include easy bruising, urinary tract bleeding (hematuria), nosebleeds (epistaxis), and bleeding into joints (hemarthrosis). The factor IX gene is located on the X chromosome (Xq27.1-q27.2). It is an X-linked recessive trait, which explains why males are affected in greater numbers. In 1990, George Brownlee and Merlin Crossley showed that two sets of genetic mutations were preventing two key proteins from attaching to the DNA of people with a rare and unusual form of haemophilia B – haemophilia B Leyden – where sufferers experience episodes of excessive bleeding in childhood but have few bleeding problems after puberty.This lack of protein attachment to the DNA was thereby turning off the gene that produces clotting factor IX, which prevents excessive bleeding. Factor IX deficiency leads to an increased propensity for haemorrhage, which can be either spontaneously or in response to mild trauma. Factor IX deficiency can cause interference of the coagulation cascade, thereby causing spontaneous hemorrhage when there is trauma. Factor IX when activated activates factor X which helps fibrinogen to fibrin conversion. Factor IX becomes active eventually in coagulation by cofactor factor VIII (specifically IXa). Platelets provide a binding site for both cofactors. This complex (in the coagulation pathway) will eventually activate factor X. The diagnosis for hemophilia B can be done via the following tests/methods: