Haemophilia B

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Haemophilia B, also spelled hemophilia 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. Most individuals who have hemophilia B and experience symptoms are men. The prevalence of hemophilia B in the population is about one in 40,000; hemophilia B represents about 15% of patients with hemophilia. Many female carriers of the disease have no symptoms. However, an estimated 10-25% of female carriers have mild symptoms; in rare cases, female carriers may have moderate or severe symptoms.

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