HoG Handbook



red blood cells and inhibitorsWhen some people take factor concentrate, their immune system makes certain proteins called inhibitors.  Inhibitors are antibodies against factor.  Although antibodies usually protect the body, inhibitors react to infused factor as something foreign.  Inhibitors interfere with the infused factor and prevent clotting.

If a person with an inhibitor has a bleed, his regular dose or type of factor will probably not stop the bleed.  Special treatment is needed.  Up to 33% of people with hemophilia A (factor VIII) may develop an inhibitor.  Up to 6% of people with hemophilia B (factor IX) may develop an inhibitor.

People likely to have inhibitors

What causes some people with hemophilia to form inhibitors is unclear at this time.  It may be genetic (inherited).  A person with a relative with an inhibitor is more likely to have one.  Most people with inhibitors have severe hemophilia.  Most of them develop inhibitors during childhood or by the time they are 20 years old.  African-Americans are also more likely to get inhibitors than white Americans.

The number of times a person takes factor does not affect his likelihood of developing an inhibitor.  Some people with hemophilia have gotten an inhibitor after very few infusions.  Other people never get an inhibitor, even though they use a lot of factor.  It is a mistake to think you can lower your chances of getting an inhibitor by using less factor.  If you don't use enough factor, all you will do is increase your risk of severe damage to your body from bleeds.

Special needs of a person with an inhibitor

Sometimes more steps are taken to prevent bleeds in children with inhibitors.  They may wear helmets and knee and elbow pads.  They may not be allowed to do some sports and activities that most children with hemophilia are allowed to do.

The inhibitor patient or parents of a child with an inhibitor may need extra emotional support.  Treating bleeds in someone with an inhibitor can be very frustrating because it may take a variety of methods and a lot of time.  If you have an inhibitor or are the parent of a child with an inhibitor, keep in close touch with your HTC.  The staff there can offer you both medical advice and emotional support for dealing with this hemophilia complication.