Inhibitor

An inhibitor is an antibody that the body develops to clotting factor protein.  An antibody is a protein that the body’s immune system makes when it does not recognize a substance.  The body is programmed to defend itself against harmful germs and viruses that it encounters.  Sometimes the body cannot tell the difference between good and bad things in the blood.  As a result, the body may fight itself or “good things” in the blood.  When the body makes an inhibitor to a clotting factor protein, that clotting factor will not work and will not be able to help make a blood clot.  This is very dangerous because the body will not be able to stop bleeding because the replacement clotting factor will not work.

Inhibitors can occur in both hemophilia A and B.  Inhibitors are more likely to occur within the first 30 doses of factor replacement, but can occur at any time in someone who has gotten factor replacement.  Blood tests can be done to check for inhibitors.  People who have inhibitors are at risk for severe complications.  Treatment for inhibitors is available.

When should an inhibitor check be done?

• After every five doses of factor administration until 30 doses are reached
• At least yearly
• Bleeding symptoms occur despite treating following the prescribed treatment plan for factor replacement
• A bleed is worsening, or stays the same, despite factor being given
• Before surgery