Inhibitors
Because people with hemophilia are missing or have too little of an important blood clotting factor, the typical treatment is to give injections, or infusions, of the factor directly into their blood to help stop or prevent bleeding. In most cases this treatment works well.
Sometimes, however, a serious complication develops in response to treatment. In some people, the body's immune system perceives the infused clotting factor as a foreign substance. The immune system fights the invader by producing antibodies, which are natural chemical substances circulating in the blood. The antibodies eliminate the infused factor concentrate, thereby preventing it from doing its job of stopping the bleeding. These antibodies are called inhibitors, because they inhibit treatment from working properly.
Who Develops Inhibitors?
Any person with hemophilia can develop inhibitors, at any age, but they are more common in young children. Most individuals who are going to develop inhibitors do so before the age of five. Inhibitors usually appear after 9 to 12 infusions with factor treatment. Generally, the more treatments a person has without developing inhibitors, the less likely they are to appear.
A person with hemophilia who has a family member with inhibitors, or is of African descent, is also at higher risk. In addition, generally people with severe hemophilia are at greater risk of developing inhibitors than those with milder forms of the disorder. The information varies, but it's estimated that approximately 20-33% of people with severe hemophilia A (less than 1% of normal factor activity) or moderately severe (1-5% of normal factor activity) will develop inhibitors to treatment.
How Are Inhibitors Identified?
A person may show signs of an inhibitor if a bleed does not respond normally or improve after 2 or 3 infusions of clotting factor, even if treatment worked previously. Tests can then be performed to confirm the presence of inhibitors. If you have a young child, it's important to be aware of the signs of inhibitors, as they require immediate attention by your healthcare team.
Treating and Managing Inhibitors
In some cases inhibitors disappear on their own, in other cases they last for many years. Fortunately, some treatment options are available. Drugs can sometimes work around the inhibitors to assist with blood clotting. Other kinds of therapies can work to remove the inhibitors. But there is no perfect treatment for inhibitors—care must be individualized to the patient, depending on their inhibitor levels, response to factor infusions, and bleed severity.
Dealing with the Challenges
Treatment of inhibitors can be very demanding, and it can take a long time to get the condition under control. Patients and their families must learn to cope with the day-to-day challenges. Babies may have to endure more treatment, while older children often miss school because of bleeds and inhibitor treatment therapies. Parents may be financially burdened when they are unable to work full-time while caring for their child and managing the various treatments they may require.
For families who previously managed living with hemophilia well and had good results with factor treatment, the development of inhibitors can make them feel angry, discouraged, fearful, overwhelmed, and very frustrated. It is extremely important to work closely with medical professionals and the local Hemophilia Treatment Centre (HTC) to get both proper treatment and emotional support.