Paediatrics: Haemophilia B

Haemophilia B

Previously known as Christmas disease. X-linked recessive disease caused by defective production of factor IX (FIX). Indistinguishable from haemo-philia A, although patients may be slower to bleed. It is five times less  common than haemophilia A.

Investigations are the same as for haemophilia A except FIX activity is deficient, rather than FVIII.

Management principles are the same as for haemophilia A except that DDAVP is of no use. Prophylaxis in patients with severe disease is with recombinant FIX therapy, usually twice a week, (FIX plasma half-life is 25hr). Generally, 1µ/kg FIX raises the plasma level by 0.7–1%. Complications and prognosis are similar to haemophilia A.