Haemophilia is a genetic (inherited) condition that affects the blood’s ability to clot.

Normally, if you cut yourself, proteins called clotting factors combine with blood cells called platelets to make the blood sticky. This makes the bleeding stop eventually.

However, in haemophilia, there are not as many clotting factors in the blood as there should be. Therefore, someone with the condition will bleed for a longer time than usual.

Find out more about the causes of haemophilia.

Haemophilia is often associated with external bleeding. However, a more common symptom is internal bleeding. This usually occurs around the joints and muscles. Internal bleeding can cause symptoms of pain and stiffness and, over time, it can damage the joints.

The symptoms of haemophilia can be mild, moderate or severe. This will affect how the condition will be treated.

The way that haemophilia genes are passed down through family members means that haemophilia almost always occurs in males.

It is essential that patients with the condition are registered at their local haemophilia centre, which is a useful source of advice and support.

Find your local haemophilia centre.

Types of haemophilia

The two most common types of haemophilia are haemophilia A and haemophilia B.

Both types have the same symptoms. However, the two types are caused by problems with different clotting factors and have slightly different treatments.

There is also a rarer form of haemophilia called acquired haemophilia. This is not an inherited condition but is caused by the immune system (the body’s natural defence against infection and illness) attacking the clotting factors in the blood.

This section is about haemophilia A and B. See the Haemophilia Society website for more information about acquired haemophilia.

Treating haemophilia

There is no cure for haemophilia. However, the outlook for the condition is generally good. This is due to major advances in treatment during the 1990s.

One of the most important developments in treating haemophilia was the creation of genetically engineered clotting factors to prevent and treat prolonged bleeding. The clotting factors can be given by regular injections.

The advantage of the newly developed medications is that they do not contain human proteins. This means that using them does not put you at risk of contracting blood-borne viruses, such as HIV or hepatitis C.

Mild and moderate haemophilia are usually treated as required. Severe haemophilia is usually treated using preventative treatment.

If it is not treated, severe haemophilia can lead to serious joint and muscle problems or potentially life-threatening internal bleeding. Some people with moderate haemophilia may also be at risk of these symptoms.

Read more about treating haemophilia.

How common is haemophilia?

Haemophilia A is the most common type of haemophilia. It is estimated that 1 boy in every 5,000 will be born with haemophilia A.

Haemophilia B is much less common than haemophilia A. It is estimated that 1 boy in every 30,000 will be born with haemophilia B.

How severe haemophilia symptoms are depends on the level of clotting factors in the blood compared to the normal amount:

• mild haemophilia – someone has 5–50% of the normal amount of clotting factors.
• moderate haemophilia – someone has 1–5% of the normal amount of clotting factors.
• severe haemophilia – someone has less than 1% of the normal amount of clotting factors.

The different severities of haemophilia are described below.

Mild haemophilia

Children born with mild haemophilia may not have any symptoms for many years. The condition usually only becomes apparent after a dental procedure, such as a filling, a significant wound or surgery. These events could cause unusually prolonged bleeding.

Moderate haemophilia

Children born with moderate haemophilia have skin that bruises very easily. They may also have symptoms of internal bleeding around their joints, particularly if they have a knock or a fall that affects their joints. Internal bleeding around the joint is known as a joint bleed.

The symptoms of a joint bleed usually begin with a tingling feeling of irritation and mild pain in the affected joint. The most commonly affected joints are the ankle joints, knee joints and elbow joints. Less commonly, the shoulder and hip joints can also be affected.

If a joint bleed is not treated, further symptoms can develop such as:

• more severe joint pain
• stiffness
• the site of the bleed becoming hot, swollen and tender

As with mild haemophilia, children with moderate haemophilia will also have prolonged bleeding after dental and surgical procedures and accidents that break the skin.

Severe haemophilia

The symptoms of severe haemophilia are similar to those of moderate haemophilia. However, joint bleeding is more frequent and severe.

Children with severe haemophilia have spontaneous bleeding. This means that they start bleeding for no apparent reason. Spontaneous bleeding can take the form of nosebleeds, bleeding gums, joint bleeds and muscle bleeding.

If they do not get treatment, people with severe haemophilia can develop:

• joint deformity, which may require replacement surgery
• soft tissue bleeding, which could lead to further complications
• serious internal bleeding

When to seek emergency medical help

There is a small risk that bleeding inside the skull can occur. This is known as an intracranial haemorrhage. It is estimated that 3% of people with moderate or severe haemophilia will have an intracranial haemorrhage.

Bleeding in the skull can be very serious and should be treated as a medical emergency. However, spontaneous bleeding inside the skull is very uncommon and usually only occurs as a result of a head injury.

The symptoms of an intracranial haemorrhage include:

• severe headache
• stiff neck
• vomiting
• a change in mental state, such as confusion
• speaking difficulties, such as slurred speech
• changes in vision, such as double vision
• loss of co-ordination
• loss of balance
• paralysis of some or all of the facial muscles

Call 999 for an ambulance if you think that you or your child has bleeding inside the skull.

Haemophilia almost always affects males due to the way it is passed down from a parent to their child.

How haemophilia is inherited

To understand how haemophilia is inherited, it is useful to know about chromosomes.

Chromosomes are blocks of DNA. They contain a detailed set of instructions that control a wide range of factors, including:

• how the body’s cells develop
• the colour of a baby’s eyes
• the baby’s sex

There are two types of sex chromosomes: the X chromosome and the Y chromosome.

All humans have a pair of sex chromosomes. Men have an XY pair and women have an XX pair.

Boys inherit their X chromosome from their mother and their Y chromosome from their father. Girls inherit an X chromosome from each parent.

Genetic mutation

Haemophilia is caused by a genetic mutation in the X chromosome. A genetic mutation occurs when the normal instructions that are carried in certain genes become "scrambled". This means that some of the body’s processes will not work in the normal way.

If a woman with the mutated X chromosome and an unaffected man have a baby girl, there is a:

• 50% chance that the baby girl will inherit a pair of normal X chromosomes and will be unaffected by haemophilia 
• 50% chance that the baby girl will inherit a normal X chromosome from her father and a mutated X chromosome from her mother

In the second circumstance, the normal X chromosome will "balance out" the mutated X chromosome. The girl will become a carrier of the mutated gene.

If a woman with the mutated X chromosome and an unaffected man have a baby boy, there is a:

• 50% chance that the boy will inherit a normal X chromosome from his mother and a normal Y chromosome from his father and will be unaffected
• 50% chance that the boy will inherit a mutated X chromosome from his mother and a normal Y chromosome from his father and will be born with haemophilia

If a man with haemophilia has a son with an unaffected woman, there is no chance that the boy will get haemophilia. This is because he will always inherit his X chromosome from his mother.

However, any daughters that the man has will become carriers of the mutated haemophilia gene. This is because girls always receive the mutated X chromosome from their father.

The type of mutation in the gene is directly connected to how severe the symptoms will be. For example, if a man with severe haemophilia has a carrier daughter who gives birth to a son with haemophilia, her son’s haemophilia will also be severe.

In some cases, a boy is born with haemophilia even though there is no family history of the condition. In such cases, it is thought that the mutation that causes haemophilia develops spontaneously in the boy’s mother, grandmother or great-grandmother but, until now, a male member of the family has never inherited the mutated gene.

Although family history is a strong indicator, some studies have shown that there was no known family history of haemophilia in up to 50% of new cases.

How haemophilia affects the blood

Blood cells called platelets are very important for blood clotting. These cells have a sticky surface that allows them to clump together to stop the flow of blood.

Platelets also need clotting agents. These are proteins that form a "web" around the platelets, helping them to stay in place.

The mutated haemophilia gene means that boys with the condition do not have enough clotting agents in their blood.

Several different clotting agents are present in the blood. They are numbered using roman numerals. For example, in haemophilia A, there is not enough clotting agent VIII (8) in the blood. In haemophilia B, there is not enough clotting agent IX (9) in the blood.

Several options are available to parents to diagnose haemophilia before, during and after birth if there is a family history of the condition.

Prenatal testing

Genetic testing and counselling are available to help determine the risk of passing the condition onto a child. These should ideally be completed before pregnancy.

If a woman with a history of haemophilia in her family becomes pregnant, it is necessary to find out the sex of the baby. This can be done either by:

• carrying out an ultrasound scan around weeks 18 to 20
• testing DNA from the mother’s blood – this is not always available but can sometimes be done as early as seven weeks into the pregnancy

If the baby is male, tests for the haemophilia gene can be carried out during the first trimester of pregnancy (weeks 0 to 12). The available tests are:

• embryo screening, known as pre-implantation genetic diagnosis (PIGD)
• chorionic villus sampling (CVS) – during CVS, a small sample of placenta is removed from the womb and tested for the haemophilia gene (find out more about how chorionic villus sampling is performed)

A small risk (1–2%) of miscarriage is associated with diagnosis through CVS in the first trimester. Discuss the risks with the doctor in charge of your care.

An alternative to CVS is a procedure called amniocentesis. This is where a sample of amniotic fluid is taken for testing late in the third trimester (weeks 35 to 36). Amniocentesis has a small chance of inducing labour (1%), but this is not known to cause any clinical problems.

Read more about amniocentesis.

After birth

If haemophilia is suspected after your child has been born, a blood test can be used to confirm the diagnosis. The blood test will also be able to identify whether your child has haemophilia A or B, and whether their condition is mild, moderate or severe.

Read more about how a blood test is performed.

If your child is diagnosed with haemophilia, their recommended treatment plan will depend on how severe their haemophilia is.

Treatment plans for haemophilia

There are two main approaches to treatment:

• treatment as required – where medication is used to stop prolonged bleeding
• preventative treatment – where medication is used to prevent episodes of bleeding and subsequent joint and muscle damage (the medical term for preventative treatment is prophylaxis)

Mild and moderate haemophilia are usually treated as required, whereas severe haemophilia is usually treated using preventative treatment.

Mild haemophilia

Cases of mild haemophilia A, where prolonged bleeding has occurred as a result of an injury or medical procedure, can be treated using a type of medication called desmopressin.

Desmopressin is a synthetic hormone. Hormones are powerful chemicals that can have a wide range of effects on the body. Desmopressin works by stimulating the production of clotting agent VIII (8) and is usually given by injection.

Possible side effects of desmopressin include:

• headache
• stomach pain
• nausea

Desmopressin is not as effective at treating mild haemophilia B. This is because this form of the condition is caused by a lack of clotting agent IX (9). Prolonged bleeding caused by an injury or medical procedure is treated with a medication called nonacog alfan (also known as Benefix).

Nonacog alfan is essentially an engineered version of clotting agent IX. It is created by cloning certain cells before joining them to other cells. The resulting product then goes through a rigorous purification process using specialised machinery.

After the purification process, the end product will contain the active ingredients needed to help the blood clot. However, it will not contain any trace of human cells or other animal cells. This means that there is no risk of contracting blood-borne viruses, such as HIV or hepatitis.

Nonacog alfan is given by injection directly into a vein. Side effects of the medication are uncommon, but include:

• dizziness
• headaches
• altered taste
• nausea
• discomfort and swelling at the injection site

Moderate and severe haemophilia

Moderate and severe haemophilia are often treated with preventative treatment. Children are usually given three injections of the clotting agent medication a week.

When your child is young, you will be trained to give them the injections. When your child is older, they will be taught to inject themselves.

Haemophilia A is treated using a synthetic version of clotting agent VIII (8), called octocog alfa. Like nonacog alfan, octocog alfa is another type of genetically engineered purified protein.

Common side effects of octocog alpha include:

• an itchy skin rash
• redness and soreness at the site of the injection

Haemophilia B is usually treated with nonacog alfan in the same way as outlined above.

Inhibitors

Inhibitors occur when the immune systems of people being treated with blood clotting agents, such as nonacog alfan, start to regard the clotting agents as foreign objects.

The immune system will start to create proteins called antibodies to block the affects of the clotting agent. These antibodies are known as inhibitors.

The inhibitors can make medication used to treat haemophilia less effective. This means it is more difficult to prevent and control the symptoms of bleeding.

An estimated 20–30% of people who have treatment for haemophilia A develop inhibitors. Around 1–3% of people who have treatment for haemophilia B develop inhibitors.

Management of inhibitors

Immune tolerance therapy (ITT)

People with moderate to severe inhibitors are usually advised to try a treatment programme called immune tolerance therapy (ITT) to overcome them.

ITT involves receiving daily injections of either octocog alfa (for haemophilia A) or nonacog alfan (for haemophilia B). Over time, the immune system should begin to recognise the blood clotting agents and stop producing inhibitors.

ITT needs to be carried out on a long-term basis. Most people require a course of treatment that lasts 6–24 months. ITT is successful in an estimated 80% of cases.

Managing a bleed with inhibitors

In people with inhibitors, the original clotting agents do not work because they are removed from the body by the inhibitors. In the event of a bleed, a "bypass agent" must be used.

A bypass agent is a separate product that can be used to stop bleeding when inhibitors are still present. ITT doesn't work in some people and they need to use bypass agents for the rest of their life.

This may cause joint damage over time because bypass agents can only be used as needed, not as preventative treatment.

Joint damage

Joint damage can sometimes occur if haemophilia is poorly controlled. Successive joint bleeds can damage cartilage (the soft spongy tissue in joints that acts as a shock absorber) as well as the synovium (a thin layer of tissue that lines the inside of the joint).

Joint damage can often develop as a "vicious circle". The more damaged a joint is, the more vulnerable it is to internal bleeding. This in turn means that the joint will become even more damaged and vulnerable to bleeding.

Joint damage is more common in older adults who have severe haemophilia. This is because modern preventative treatments were not available in the past. It's hoped that modern treatments mean that children growing up today with haemophilia will not have joint damage.

Surgery can be used to treat joint damage. The procedure involves removing the damaged synovium to allow new synovium to grow in its place. If a joint is very seriously damaged, it may be necessary to replace the whole joint with an artificial one, such as a hip replacement or knee replacement.

To get the most out of your appointment with a healthcare professional, these are the questions you need to ask

Before you leave your appointment

Before you leave your appointment, make sure you know the following:

What might be wrong?

You could ask the following questions:

• Can I check that I've understood what you've said? What you're saying is...
• Can you explain it again? I still don't understand
• Can I have a copy of any letters written about me?

What about any further tests, such as blood tests, scans and so on?

You could ask the following questions:

• What are the tests for?
• How and when will I get the results?
• Who do I contact if I don’t get the results?

What's the best treatment for you?

• Are there any other ways to treat my condition?
• What do you recommend?
• Are there any side effects or risks?
• How long will I need treatment for?
• How will I know if the treatment is working?
• How effective is this treatment?
• What will happen if I don't have any treatment?
• Is there anything I should stop or avoid doing?
• Is there anything else I can do to help myself?

What happens next?

• What happens next? Do I come back and see you?
• Who do I contact if things get worse?
• Do you have any written information?
• Where can I go for more information, a support group or more help?