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Haemophilia A

Haemophilia A is a bleeding disorder where a protein made by the body to help make blood clot is either partly or completely missing. This protein is called a clotting factor: with haemophilia A there is a deficiency of clotting factor VIII (eight).

Haemophilia A is a genetic condition and nearly everyone who has it was born with it. In around two thirds of cases there is a family history of haemophilia A.

Haemophilia A mainly affects boys and men. Women can be ‘carriers’ of the affected gene and may experience symptoms. Although it is the most common type of haemophilia it is a rare condition, affecting about one in every 10,000 people.

Haemophilia A is classed as mild, moderate or severe, depending on the level of clotting factor VIII in the blood. It is diagnosed through blood tests.


The main symptoms are:

  • a tendency to bruise easily especially in early childhood
  • excessive bleeding from cuts that takes a long time to stop
  • a tendency to bleed into joints and muscles causing pain, swelling and limitation of movement

Haemophilia A is treated by replacing the missing clotting factor VIII in the blood through an intravenous infusion of clotting factor concentrate. In the UK most people with haemophilia A are treated with manufactured clotting factor concentrate (recombinant) although it can be made from human blood plasma as well (plasma derived).

Bleeding episodes must be treated promptly to avoid lasting effects. Once the bleeding stops, pain rapidly diminishes and, in the case of limbs, full use returns.

With the right treatment and care, people with haemophilia A can lead fulfilled and healthy lives into old age. However, there is currently no cure for haemophilia A.

You can read our booklet on understanding Haemophilia on our publications page.