Hemophilia B

Hereditary coagulation disorder caused by defective synthesis of plasma protein factor IX.

Christmas Disease; F-IX Deficiency.

Also called Christmas disease after Steven Christmas, who was first diagnosed with the disease at 5 years of age in 1952 (and who died of AIDS at age 46 in 1993). Sir Jonathan Hutchinson was responsible for naming clinical disorders after patients and has become familiar for serologic research.

1:40,000 males (15-20% of hemophiliacs).

X-linked. Defective coagulation factor IX. Gene map location is Xq27.1-q27.2.

Factor IX is a vitamin K-dependent clotting factor. It is activated by either factor XIa or factor VIIa-tissue factor complex. Once activated, it activates factor X in the presence of calcium, phospholipid, and factor VIIIa. Because deficiency of factor VIII or factor IX decreases factor X activity, hemophilia B is clinically indistinguishable from hemophilia A. Affected patients are classified as mild, moderate, or severe. Mildly afflicted patients have factor IX levels 5 to 40% of normal activity, moderately afflicted patients have levels 1 to 5% of normal activity, and severely afflicted patients have less than 1% of normal activity.

Based on assays of factor IX antigen and factor IX activity. According to the residual factor IX activity, the disorder is classified as severe (<1%), moderate (1 to 5%), or mild (5-20% of normal value). Prenatal and carrier detection are possible with restriction fragment length polymorphism DNA analysis but are contingent upon parental analysis. Elevation of the partial thromboplastin time with normal prothrombin time and bleeding times are found.

Early onset of symptoms: increased tendency to bleeding becomes evident in 90% of affected patients by 1 year of age. Clinical picture very similar to hemophilia A, namely, soft tissue hematomas, including retroperitoneal/pharyngeal hemarthroses (75%), often at the same target joint, pseudotumor of bone, with rare erosion into viscera, hematuria, intracranial hemorrhage, cord compression secondary to epidural bleeding, nerve compression secondary to hematoma, mucous membrane hemorrhage (epistaxis, hemoptysis), peptic ulcer disease, and excessive postsurgical bleeding. Hepatitis infection from previous transfusions is common.

Hematology and anesthesiology consultation are highly recommended before elective surgical procedures. Schedule surgical procedures early in the week to avoid pharmaceutical delays. Ensure supply of virally inactivated factor IX concentrate, which does not have the infectious risks of fresh-frozen plasma. Dose calculations are based on the following formula: 1 unit factor IX/kg increases factor IX activity by 1%. Half-life is 18 to 24 hours. Consider antifibrinolytic therapy [epsilon-aminocaproic acid (EACA), tranexamic acid or aprotinin] because these agents may be useful adjuvants for dental bleeding. Raise factor IX to normal levels before major surgical procedures.

In conjunction with a hematologist consultation, maintain factor IX levels periand postoperatively. Avoid regional anesthesia and intramuscular injections.

Avoid aspirin and NSAIDs.

Hemophilia A: More severe hereditary coagulation disorder but otherwise a clinically similar syndrome caused by ...