Factor IX deficiency (hemophilia B) was first described in the 1950s by British doctors caring for a young boy. That child, who later went on to have a disease and clotting factor named in his honor, was Stephen Christmas.
A defective gene causes Christmas disease on the X chromosome, either inherited (in most cases) or due to spontaneous mutations during development. Due to X-linked inheritance and a defect of the intrinsic coagulation cascade, the typical presentation is a male with “spontaneous bleeding” (especially into muscles/soft tissues), hemarthrosis, and excessive bleeding after trauma. Family histories are very helpful, but the diagnosis is confirmed with clotting factor assays showing a deficiency of factor IX. Naturally, it follows that the severity of symptoms (mild, moderate, and severe) trends with the degree of plasma factor IV concentration compared to normal values (< 50%, < 5%, < 1%, respectively).
In patients with known Christmas disease presenting with bleeding, treatment trumps additional testing (ie, head CT). The recommendation is to administer recombinant factor IX whenever possible as it’s safer than FFP and gives patients back exactly what they are missing. Remember that although cryoprecipitate contains factor VIII and is therefore a potential therapy for hemophilia A, it does NOT contain factor IX.
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