Hereditary deficiency of factor IX transmitted associated an X-linked pattern.
Less common than Hemophilia A with a prevalence of 5.3 per 100,000 male births in the U.S. , 1 in 30,000 live male births.
30% of cases are sporadic.
Clinically indistinguishable from Hemophilia A and associated with soft tissue, joint, posttraumatic and surgical bleeding.
Life expectancy about 65 years.
Patients have a prolonged partial thromboplastin time which corrects with mixing studies.
Factor IX activity levels correlate with disease severity.
Caused by a deficiency or dysfunction of factor IX.
4-6 times less prevalent than factor VIII deficiency.
Severe, moderate and mild disease reflect levels of <1%, 1-5% and >5-40%, respectively.
Prothrombin time, platelet count, thrombin time, von Willebrand factor and factor VIII levels are normal.
Both plasma derived and recombinant forms of factor IX are available for therapeutic and prophylactic management.
Factor IX is distributed equally between the intravascular plasma compartment and extravascular space so that the administration of 1 unit of factor IX per kg raises the plasma activity by 1%.
Plasma half-life of factor IX is 18-24 hours and replacement dosing should be done at the same intervals.
Management for acute bleeding and prophylaxis are similar for Hemophilia A.
The development of alloantibody inhibitors occurs infrequently at about 1-3% of cases.
Rarely the administration of factor IX containing products in patients with anti-factor IX alloantibody inhibitors can trigger anaphylactic like reactions, therefore in the presence of inhibitors factor VIIa is the treatment of choice when replacement treatment is needed.
it was common among the descendants of Queen Victoria.