Inhibitors can vary in severity in the same person. Doctors do not know exactly why inhibitors develop in some hemophiliacs and not in others. They think there are 2 possible causes. The first possible cause is environmental. This is external to the hemophiliac.
Doctors think that something in the factor concentrate triggers the body s immune system to react.
For this reason, many doctors who treat hemophiliacs prefer to switch concentrate brands as rarely as possible. If a product is working well, and has not caused inhibitors to develop, doctors won t recommend a switch to a different product unless there is a very good reason. The second possible cause is genetic. Some hemophiliacs with a certain type of mutation of their Factor VIII gene may be more prone to developing inhibitors. This explains why development of inhibitors sometimes runs in a family.