What is haemophilia?
In haemophilia, the blood's ability to clot is severely reduced because an essential clotting factor - a chemical within the blood - is partly or completely missing. This means that people bleed for longer than normal.
There are two types of haemophilia:
- Haemophilia A - a deficiency of an essential clotting factor called factor VIII, which is normally produced in the liver. The faulty gene that causes haemophilia A is found on the X chromosome (X-linked). The faulty gene is found on the X chromosome (X-linked). It's five times more common than haemophilia B.
- Haemophilia B - a deficiency of clotting factor IX and also X-linked. Quite often there is no family history and the disorder is a new development because of a new genetic mutation.
In Von Willebrand's disease there are either low levels of a protein called von Willebrand factor in the blood, or the protein doesn't work the way it should. There are three different types of the disease, which is due to a mutation not on the X-chromosome but chromosome 12. There are both autosomal recessive and dominant forms. Spontaneous mutations aren't uncommon, so no-one else in the family may be affected.
Haemophilia symptoms
Symptoms range from easy bruising to prolonged bleeding. Bleeds can occur spontaneously (without an external cause) or as a result of injury.
How easily or badly a person bleeds depends on the severity of their deficiency. Minor cuts and grazes don't usually cause any significant problems, but internal bleeding can be life threatening, while repeated bleeding in the joints typically leads to arthritis or long-term joint damage.
Mobility problems may also result from these spontaneous bleeds. Haemorrhages into the brain are particularly difficult to manage and can be fatal.
Education and employment may also be disrupted, especially when haemophilia is severe.
Haemophilia causes
Haemophilia is an X-linked recessive disorder. Women have two X chromosomes while men have one X and one Y chromosome. This means that most people with the condition are male- if a woman inherits the abnormal gene from her mother she will still have a normal X chromosome from her father but a man has only one X chromosome so if it contains the faulty gene there is no normal chromosome to counter it.
Women who carry the faulty gene on one of their two X chromosomes will still be carriers and can pass the disease on to their children. Occasionally, a woman inherits two faulty X chromosomes from her parents, in which case she will have haemophilia.
Although it's inherited, in around one in three cases of haemophilia there's no family history of the disease, and it may take longer for the problem to be identified.
There are about 6,000 people in the UK with haemophilia. About 5,000 people have been diagnosed with Von Willebrand's disease, but its thought that many mild cases go undiagnosed and it may affect as many as 1 in 100 people. Genetic counselling and antenatal screening of families with haemophilia is an opportunity to prevent these diseases being passed on to children.
Carriers of the gene can be identified with a blood test. Pregnant women can be assessed using ultrasound to determine the sex of the baby and so estimate the risk of the disease. They can then decide whether to have more invasive tests - amniocentesis and CVS - which can detect the relevant gene in the baby.
Haemophilia treatments
There's no cure for haemophilia and, although patients are treated with injections of the missing clotting factor, there's no permanent way of increasing its level.
So the mainstay of treatment is replacement of the missing clotting factor. This is known as replacement therapy and these days, in most countries including the UK, it usually consists of injections of concentrates of artificially produced clotting factors (made using recombinant technology, rather the old method of extracting the clotting factors from donated blood).
In severe haemophilia injections may be given on a regular basis several times a week. This is called prophylaxis, and it aims to help prevent bleeding from happening. In mild or moderate haemophilia injections are given just when a bleed has or may have occurred (this is called on-demand therapy).
If a person known to have haemophilia has a bleed, immediate measures - such as resting quietly and splinting the joint or limb - will reduce the amount of blood lost, but they need specialist management, including treatment with factor VIII or IX concentrate.
People with the condition will often keep a supply of clotting factor in the fridge at home. They should also known where their nearest appropriate treatment centre is, as this may not be at their local hospital.
If someone you know is a haemophiliac, it's worth checking with them about what they need and where their local supply and treatment centres are in case of emergency.
In the past there have been very serious problems with blood products contaminated with infections such as HIV and Hepatitis, which have resulted in fatal infections in people with haemophilia. With the introduction of recombinant factors, the risks from donated blood , have mostly been resolved. Concern still remains about possible vCJD infection from past treatments using blood products, but most well-managed haemophiliacs should expect to enjoy a lifestyle and longevity similar to that of their peers.
Another medication, known as desmopressin, may also be used in some instances to try to raise the body’s own levels of the missing clotting factors, especially before planned surgery or dentistry.
