Hemophilia B

Hemophilia B is a disorder of the blood

Pathophysiology

1) congenital bleeding disorder caused by deficiency in factor 9 2) factor 9 is synthesized in the liver and requires vitamin K for biologic activity 3) clinically indistinguishable from hemophilia A, but treatment is different

Biochemistry

factor 9 is converted to its active form factor 9A by factor 11A or the factor 7A-tissue factor complex

Inheritance/Epidemiology

1) occurs in 1/100,000 in males 2) X-linked inheritance

Treatment

1) fresh frozen plasma (FFP) 2) monoclonal factor 9 preparation 3) prothrombin complex concentrates have been used but can cause embolism and thrombosis

Tips for USMLE

1) inhibitors to factor 9 do occur but much less frequently than in factor 8 deficiency (hemophilia A) 2) hemophilia A and B both have increased PTT, normal PT, normal bleeding time, and normal platelet count 3) differentiation between hemophilia A and B requires specific assays to detect absence of clotting factors 8 or 9