How common are inhibitors and are there differences between haemophilia A and B?
It is estimated that up to one third of people with severe or moderately severe haemophilia A (less than 5% clotting factor) may develop an inhibitor at some time in their lives. However, among people with haemophilia B, inhibitors seem only to affect less than 5% of people with severe or moderately severe haemophilia. Inhibitor development is rare among people with mild haemophilia. It is thought that inhibitors may run in families, although having one child or adult with an inhibitor in a family does NOT mean that other family members will necessarily get one. The risk of developing inhibitors does not remain the same throughout the life of the person. Historically inhibitors have tended to develop more frequently during childhood, when treatment begins. This is also the time at which the body is making most antibodies to childhood illnesses and the immune system reacts as if factor VIII or IX is a protein that it should fight. High and low titres – What do they mean? The presence of
