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What is haemophilia A?
Haemophilia A is a rare inherited bleeding disorder caused by a deficiency of clotting factor VIII, a protein that plays a crucial role in the blood clotting process.
In people with haemophilia A, the blood does not clot properly after an injury. As a result, bleeding may last longer than usual and, in some cases, may occur spontaneously without any obvious cause.
Haemophilia A is the most common form of haemophilia, accounting for approximately 80–85% of all haemophilia cases worldwide. Like other forms of haemophilia, it is usually a genetic condition inherited through the X chromosome.
Because men have only one X chromosome, they are more likely to develop the disease if they inherit the mutated gene. Women usually have two X chromosomes and are therefore most often carriers of the gene, although some may experience mild bleeding symptoms.
Although haemophilia A is a lifelong condition, advances in medical treatments have significantly improved the outlook for people living with the disorder. With appropriate treatment and regular medical care, many individuals with haemophilia A can lead active and fulfilling lives.
What are the symptoms of haemophilia A?
The symptoms of haemophilia A vary depending on the severity of factor VIII deficiency.
People with mild haemophilia A may only experience bleeding after surgery, dental procedures, or major injuries. In more severe cases, bleeding episodes may occur more frequently and sometimes spontaneously.
Common symptoms include:
- prolonged bleeding after cuts, injuries, or medical procedures
- frequent or unexplained bruising
- bleeding into joints, known as haemarthrosis, which can cause pain, swelling, and reduced mobility
- bleeding into muscles
- frequent nosebleeds
- excessive bleeding in infants following medical procedures
Joints such as the knees, ankles, and elbows are particularly affected by repeated bleeding episodes.
Over time, repeated bleeding into joints can lead to chronic joint damage, known as haemophilic arthropathy, which may cause pain, stiffness, and reduced mobility.
What causes haemophilia A?
Haemophilia A is caused by a mutation in the F8 gene, which provides instructions for producing clotting factor VIII.
This gene is located on the X chromosome, meaning the condition follows an X-linked inheritance pattern.
When a male inherits the mutated gene, he will develop haemophilia A. Women who inherit the mutation usually become carriers, although some may have mild symptoms due to lower levels of factor VIII.
In some cases, haemophilia A occurs without any known family history, as a result of a spontaneous genetic mutation.
There is also a rare condition called acquired haemophilia A, which develops when the immune system produces antibodies that attack clotting factor VIII. Unlike inherited haemophilia, this form is not genetic.
How is haemophilia A diagnosed?
Haemophilia A is diagnosed through blood tests that evaluate the blood’s ability to clot and measure clotting factor levels.
When unusual bleeding is suspected, doctors may perform several laboratory tests, including:
- clotting time tests
- measurement of factor VIII activity levels
- genetic testing to identify the mutation responsible for the disorder
In families with a known history of haemophilia, screening may be performed early in life or during pregnancy.
Early diagnosis is important because it allows healthcare professionals to start treatment promptly and prevent complications associated with repeated bleeding episodes.
What treatments are available for haemophilia A?
Although haemophilia A cannot yet be permanently cured in most cases, modern treatments allow doctors to effectively prevent and control bleeding episodes.
Treatment generally involves replacing the missing clotting factor VIII through intravenous infusions.
Two main treatment approaches are used.
On-demand treatment
In this approach, factor VIII is administered when a bleeding episode occurs, helping to stop the bleeding quickly and prevent complications.
Preventive treatment (prophylaxis)
Preventive treatment involves regular infusions of clotting factor VIII to prevent bleeding episodes from occurring.
In recent years, several innovative treatments have been developed, including:
- extended half-life factor VIII therapies, which allow less frequent injections
- bispecific antibodies that mimic the function of clotting factor VIII
- gene therapy, a promising new treatment designed to address the genetic cause of haemophilia A
These advances have greatly improved long-term outcomes for people living with haemophilia A.
Possible complications of haemophilia A
If haemophilia A is not properly managed, repeated bleeding episodes can lead to several complications.
The most common complications involve joint damage, caused by repeated haemarthrosis. This can result in chronic pain, stiffness, and reduced joint mobility.
Other potential complications include:
- severe muscle bleeding
- internal bleeding
- in rare cases, life-threatening bleeding in the brain
With appropriate treatment and regular medical monitoring, the risk of severe complications can be significantly reduced.
Living with haemophilia A
Living with haemophilia A often requires adapting certain aspects of daily life to reduce the risk of bleeding.
With proper treatment and medical supervision, many people with haemophilia A can maintain an active lifestyle.
Effective management usually involves:
- regular follow-up in specialised haemophilia treatment centres
- learning how to recognise and manage bleeding episodes
- practising safe and appropriate physical activities that strengthen muscles and protect joints
- taking precautions to prevent injuries
Education about the condition is essential for patients and their families, helping them better understand the disease and respond quickly to bleeding episodes.
In addition, support from other people living with haemophilia can be extremely helpful. Sharing experiences and advice can help patients better manage the condition and reduce feelings of isolation.
FAQ about haemophilia A
What is the difference between haemophilia A and haemophilia B?
Haemophilia A is caused by a deficiency in clotting factor VIII, while haemophilia B is caused by a deficiency in factor IX.
Is haemophilia A hereditary?
Yes, in most cases haemophilia A is an inherited genetic condition linked to the X chromosome.
Can haemophilia A be cured?
There is currently no definitive cure for haemophilia A, but modern treatments allow patients to manage the condition effectively and prevent bleeding episodes.
What is the life expectancy for someone with haemophilia A?
With appropriate treatment and medical care, the life expectancy of people with haemophilia A is now close to that of the general population.
Can people with haemophilia A play sports?
Yes, certain physical activities are encouraged because they help strengthen muscles and protect joints. However, high-impact or contact sports may need to be avoided.
Last updated: 05/03/2026
