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An inhibitor is a type of antibody that prevents factor replacement treatment from working. When an inhibitor develops, it binds to factor concentrates such as factor VIII or factor IX, stopping them from working and making bleeding more difficult to treat.

Of people with severe haemophilia A, about 30% will develop inhibitors; among those with mild and moderate haemophilia A the figure is about 9%. However, only 3% of people with haemophilia B will develop an inhibitor.

Known risk factors in the development of inhibitors include:

  • severity of the bleeding disorder
  • ethnicity
  • family history of inhibitors
  • number of days treated with clotting factor concentrate

Inhibitors typically develop in the first 50 treatment ambien genericdays, with most developing in the first 20 days. This is why when people with severe haemophilia develop inhibitors it is usually during childhood, whilst people with mild or moderate conditions tend to develop them later in life.

Inhibitors are treated with immune tolerance therapy (ITT). ITT involves regular exposure to factor treatment with the aim of the body becoming accustomed to the clotting factor. Studies show that by flooding the system with factor VIII or factor IX the body often stops rejecting it.

It is recommended that children with inhibitors start ITT therapy as early as possible, and usually continue without interruption for 12 months or longer.

Inhibitor survey

Thank you to everyone who took part in our Inhibitor Survey. We will use the survey information to campaign for people with bleeding disorders and inhibitors and to help develop resources, information and services specifically for people affected by an inhibitor.

We are working on the survey results and will share these with you soon. We are also planning to hold an inhibitor conference in March, so look out for more news on the details of this event in the next few weeks.

More Information

More information on Inhibitors can be found on the European Haemophilia Consortium Inhibitor website.