Infectious complications are associated with the human origin of certain blood products used in the treatment of haemophilia B. In the past, viral transmission (HIV, hepatitis B and C) was a major complication of haemophilia B therapy, but since the introduction of effective viral inactivation processes towards the end of the 1980s, this risk has become minimal.
Immunological complications are due to immunisation of patients undergoing treatment with factor IX concentrates. The resulting antibodies neutralise factor IX and render it ineffective within minutes. In one third of patients, these antibodies are transient and disappear within several days to weeks, whereas in others they subsist at varying levels. The presence of antibodies directed against factor IX may require the use of alternative therapeutic solutions.
These antibodies are present in between 1 and 3% of patients with haemophilia B.
In children, screening for these inhibitory antibodies should be carried out every 3 to 12 months or every 10 to 20 days during exposure, whichever is first. In adults, screening depends on clinical requirements.
Osteoarticular complications result from the high frequency of haemarthrosis and cause gradual loss of function as well as mechanical and inflammatory pain. Such lesions can occur very early and may be seen in children.
50% of haemophilia B patients with an inhibitor may present serious allergic reactions, including anaphylactic shock on administration of factor IX.