Acquired haemophilia is a very rare condition, occurring in only 1-2 people in a million.

What is…

Acquired haemophilia is a very rare condition, occurring in only one to two people in a million. It can affect males and females. Normally blood forms a clot after injury or surgery, through a complex process of chemical reactions involving a number of different proteins, or clotting factors. One of these clotting factors is called factor VIII (8), which is necessary for blood to clot normally.

In acquired haemophilia, the production of factor VIII is normal, however the persons immune system starts to destroy their own factor VIII causing low levels of factor VIII, which may cause bleeding for no apparent reason. This condition is not passed on through families, unlike congenital haemophilia, because the gene for factor VIII is normal.

Most cases of acquired haemophilia are due to destruction of factor VIII, however it is possible for other clotting factors, such as factor IX and Von Willebrand factor, to be affected in a similar way.

In over 50% of cases of acquired haemophilia, the cause is never established. It may be associated with other illnesses such as rheumatoid arthritis, ulcerative colitis, asthma, psoriasis and cancer. Very rarely it can be triggered by a reaction to some medicines or pregnancy.

The immune system (made up of some of the blood cells, the lymph glands and the spleen) protects the body from bacteria, viruses and other proteins that the body regards as foreign. One of the ways it does this is to make antibodies (proteins), which destroy the foreign “invaders”.

In acquired haemophilia, the immune system starts to regard the body’s own factor VIII as foreign and makes an antibody to destroy it. This antibody is also known as the inhibitor because it stops the factor VIII from working properly.