An inherited coagulation disorder resulting from a factor IX deficiency.
1 in 30,000.
X linked; males only affected.
Mutations on the X chromosome including deletions, point mutations and insertions. Factor IX is the last com-ponent of the intrinsic pathway .
Similar to haemophilia A with mild deficiency causing only bleeding post surgery and trauma. Severe deficiency presents in early life with recurrent joint and muscle bleeds.
Activated partial thromboplastin time is raised, but correctable with 50% normal serum (i.e. not due to an inhibitor of coagulation) other coagulation measures are normal.
Factor XI levels are low.
Treated with factor IX concentrates. Patients who develop antibodies to factor IX concentrates may be successfully treated with recombinant factor VIIa.