Although most factor concentrates are very effective in stopping bleeding, some people with haemophilia develop antibodies called inhibitors to the concentrates, making them ineffective. When inhibitors develop the body begins recognising the concentrate as a foreign agent, like it would an unknown bacteria, and eliminates it before the factor can perform its job forming a blood clot. Bleeding can no longer be controlled quickly and there is a risk of permanent damage from bleeding into the joints or death from serious internal bleeding.
Inhibitors and Haemophilia A
Inhibitors affect 1 in 5 people with severe haemophilia A, usually when they are very young but can also develop later in life. Inhibitors also develop in about 1 in 15 people with mild or moderate haemophilia A, usually during adulthood. Some people may be more disposed to developing inhibitors; however exactly why they develop still requires research. Inhibitor severity varies greatly, even within the same person. For many the inhibitors disappear on their own within an average of 9 months, while in others they persist and require intensive long-term Immune Tolerance Therapy (ITT) which consists of large daily doses of Factor VIII and/or the intake of other products to weaken the body’s immune response. Alternative products aimed at stopping bleeding are also sometimes prescribed such as recombinant Factor VIIa or desmopressin.
Inhibitors and Haemophilia B
Inhibitors are rare in haemophilia B and only affect approximately 1 in 100 people. In most cases, the inhibitors develop after the first infusions of Factor IX concentrate. Inhibitors in people with haemophilia B can be extremely serious as ITT does not appear to work well and can be accompanied by severe allergic reactions. Recombinant Factor VIIa can be prescribed as an alternative treatment.
Support for families dealing with inhibitors
Both the person with inhibitors and their family face many challenges as the ongoing struggles with haemophilia are intensified. HFNZ recognise that these people and their families have special support and education needs. Along with our Outreach service, HFNZ also run Inhibitor Workshops specifically for these families. It provides them a chance to get together, better understand and find ways of coping with the unique challenges they face.
"The Inhibitor Workshop was awesome in increasing knowledge about my son's condition, helping make better informed choices and meeting others in a similar situation - building a greater support network for us."