About haemophilia


Haemophilia is a type of bleeding disorder in which the blood does not clot properly. Being diagnosed with a chronic illness like haemophilia can come as a shock, but haemophilia is a manageable condition. Appropriate management will help enable a full, healthy and active life to be lived, with the same access to opportunities as anyone else. 

Understanding haemophilia will empower you to have effective conversations with healthcare professionals and give you the confidence to help you and your family lead as normal a life as possible. Find out more about haemophilia on this page and download our helpful guides for parents and guardians

What is haemophilia?

When a person with haemophilia bleeds it takes longer than normal for the bleeding to stop. This is because people with haemophilia don’t produce enough of an important protein that helps the blood to clot, called a ‘clotting factor’. Haemophilia is a rare disease that is usually inherited and is more common in males than females.

Types of haemophilia

There are two types of haemophilia: haemophilia A and haemophilia B. In haemophilia A there is a lack of clotting factor VIII (eight) and in haemophilia B there is a lack of clotting factor IX (nine). Haemophilia A affects around 1 in 5,000 male births, while haemophilia B is less common and only affects around 1 in 25,000 male births. Both types of haemophilia occur mainly in males.

Haemophilia A and B are usually inherited conditions. In rare cases, haemophilia can occur without a family history due to a change in the person’s own genes. Around 30% of people with haemophilia A or B have this sporadic form.

Levels of severity

The severity of haemophilia usually depends on the amount of clotting factor present in the blood. Most cases of haemophilia are severe.

  • Severe haemophilia: the level of clotting factor in the blood is less than 1% of the normal level
  • Moderate haemophilia: the level of clotting factor in the blood is between 1–5% of the normal level
  • Mild haemophilia: the level of clotting factor in the blood is between 5–40% of the normal level

People with severe haemophilia can bleed frequently and often for no apparent reason. This is known as spontaneous bleeding and occurs most commonly in the joints or muscles. People with moderate haemophilia usually bleed less frequently than those with severe haemophilia, and do not usually bleed spontaneously. They may bleed for a long time after injury, surgery or dental procedure. People with mild haemophilia usually only have prolonged bleeding after serious injury or surgery and may never bleed spontaneously.

Find out more about different types of bleeding.

The inheritance of haemophilia

Haemophilia is usually caused by inheritance of a damaged or ‘mutated’ gene from the parents. People with haemophilia can’t produce enough clotting factor because of this damaged gene. 

The genes that carry the code for clotting factors are found on X chromosomes. Men only have one X chromosome while women have two. This means that men who inherit the damaged gene always develop haemophilia. If a woman inherits the damaged gene she will become a ‘carrier’ — she will have one damaged and one normal copy of the gene. Female carriers of haemophilia are not usually affected by the disease, although some do have symptoms of mild haemophilia, but they can pass the damaged gene on to their children. 

When a mother is a carrier and the father does not have haemophilia, there is a 50% chance that each son will have haemophilia and a 50% chance that each daughter will be a carrier. When a father has haemophilia and the mother is not a carrier, no sons will inherit haemophilia but all daughters will be carriers of the damaged gene. 

Inheritance of haemophilia in families

In extremely rare cases it is possible for a daughter to inherit haemophilia. This happens when the father has haemophilia and the mother is a carrier so the daughter inherits the affected X chromosome from both parents.

How is haemophilia diagnosed?

Most people with haemophilia have a family history of the condition and so it will be suspected and diagnosed at birth. If there is no family history, which is the case for people who have the sporadic form of haemophilia due to new genetic mutations, diagnosis may take longer. Diagnosis may also be delayed if the family is not aware that there is a family history. For example, if previous generations in the family have only had daughters who are carriers without symptoms or had sons who died in early childhood from undiagnosed haemophilia.

Severe haemophilia is usually diagnosed in the first few months of life because it can cause serious bleeding problems from birth. People with mild or even moderate haemophilia may not be diagnosed for many years, even into adulthood, possibly as a complication of surgery.

Diagnosis is made with a series of blood tests to measure the level of clotting factor activity. If there is a known family history of haemophilia, this testing can be done during pregnancy. Genetic testing may also be performed to look at the specific mutation that is causing the haemophilia.

What happens when you bleed?

Normally, the body reacts to bleeding by triggering a series of events that help the blood to clot. Proteins called clotting factors interact with each other to form a clot that stops the bleeding.

Take a look at how clotting factors work together to stop bleeding

People with haemophilia lack an essential clotting factor, so when they start to bleed a disruption occurs in the clotting process. In haemophilia A there is a lack of clotting factor VIII (eight) and in haemophilia B there is a lack of clotting factor IX (nine). By administering medication containing the missing clotting factor, the clot formation process can be restored. 

Types of bleeding

Bleeding in people with haemophilia can happen anywhere in the body, including beneath the skin. Bleeds inside the body are most commonly in the joints or muscles and may occur for no apparent reason. This spontaneous bleeding usually only happens in severe haemophilia. Spontaneous bleeding in the joints typically affects the ankles, elbows and knees, and often appears around the age of one, when the child starts to walk and move around. 

Signs of bleeding in the joints are pain, stiffness, warmth and swelling. Muscle bleeding is usually more difficult to see; the muscles are located so far beneath the skin that bruising is not visible. Common signs are pain and restricted movement.

Bleeding in the head or brain is rare but particularly serious as it can cause seizures and paralysis. Signs include a severe headache, stiff neck, vomiting and confusion. You should call an ambulance if you suspect it. You should also contact a healthcare professional following any severe blows to the head.  

If you suspect internal bleeding it is always best to seek advice from a healthcare professional, especially in the beginning when you may not be familiar with all the signs. 

Bleeding in haemophilia is managed by replacing the deficient clotting factor. This may be done during a bleed or regularly to try and prevent bleeding episodes from occurring and to allow the person to lead a full and normal life. Find out more about living with haemophilia

Long-term effects of haemophilia

Older people living with haemophilia A and B who did not begin prophylactic treatment at a young age often have disabilities caused by immobility and joint pain that can impact on their quality of life and independence.

However, the availability of effective treatment and long-term management today means many people with haemophilia can now have a normal life expectancy and good quality of life. Find out more about living with haemophilia.