Hemophilia B

n. (Haematology) Hemophilia B, hereditary blood coagulation disorder, form of haemophilia caused by congenital deficiency of clotting factor IX in the blood

Haemophilia B (also spelled Hemophilia B or Hæmophilia B) is a blood clotting disorder caused by a mutation of the Factor IX gene. It is the second most common form of haemophilia, rarer than haemophilia A. It is sometimes called Christmas disease after Stephen Christmas, the first patient described with this disease. In addition, the first report of its identification was published in the Christmas edition of the British Medical Journal.
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Hemophilia B n. A clotting disorder of blood resembling hemophilia A, caused by hereditary deficiency of factor IX. Also called Christmas disease. [more]Hemophilia B - Community and Resources

Noun
1. a clotting disorder similar to hemophilia A but caused by a congenital deficiency of factor IX
(synonym) haemophilia B, Christmas disease
(hypernym) hemophilia, haemophilia, bleeder's disease

Also called Christmas disease (so-named for the first patient studied in detail with the disease). Due to deficiency of coagulation factor IX. The hemophilia B gene is also on the X chromosome.