Complications of clotting factor replacement therapy

Development of Inhibitor

Inhibitors are antibodies to clotting factors VIII and IX. They are made by the body’s immune system and attack and destroy the factor VIII and IX proteins in clotting factor concentrates, making treatment ineffective. It is most common in children with severe Haemophilia A. Around 30% of boys with haemophilia A develop inhibitors and around 4% of boys with haemophilia B develop inhibitors. Boys are regularly screened for the presence of inhibitor using a blood test. Treatment is available and the aim of treatment is to stop the body producing the inhibitor. Treatment involves intensive high dose treatment with the clotting factor concerned and sometimes immunomodulating drugs. This therapy regime may involve the use of daily or twice daily injections of factor concentrate for up to a year or even longer in some cases. The inhibitor cannot always be treated and in these cases factor concentrate does not work. Other treatments can be given that help to stop bleeding but they are less effective. Progressive joint damage is likely and disability is more likely to be present in a child with an inhibitor than in a child without.

Blood borne diseases

No-one with haemophilia in the UK has been infected with Hepatitis B, C or HIV via blood products since 1986. There is a theoretical risk of infection with variant Creutzfeld–Jacob disease (variant CJD) but to date there have been no cases.