Haemophilia is an inherited condition that affects the blood's ability to clot.
Normally, when you cut yourself, substances in the blood known as clotting factors combine with blood cells called platelets to make the blood sticky. This makes the bleeding stop eventually.
However, in haemophilia, there aren't as many clotting factors as there should be in the blood. This means that someone with the condition bleeds for longer than usual.
The condition is passed to a child by one or both of their parents.
Read more about the causes of haemophilia.
How it affects you
The symptoms of haemophilia can be mild to severe, depending on the level of clotting factors you have. Most cases are mild, but people with severe haemophilia experience symptoms, which require ongoing care.
People with severe haemophilia often experience internal bleeding. This usually occurs around the joints and muscles, causing pain and stiffness. It can also lead to joint damage over time.
Read more about the symptoms of haemophilia and complications of haemophilia.
Types of haemophilia
The two most common types of haemophilia are haemophilia A and haemophilia B, although haemophilia A accounts for the majority of cases.
Both types have the same symptoms, but they're caused by problems with different clotting factors and have slightly different treatments.
There's also a rarer form of haemophilia called acquired haemophilia. This isn't 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.
These pages are about haemophilia A and B.
Who is affected?
There are about 6,000 people with haemophilia in the UK. Most of these are males because of the way the condition is inherited.
Worldwide, it's estimated that one boy in every 5,000 will be born with haemophilia A and one boy in every 30,000 will be born with haemophilia B.
However, some females who carry the haemophilia gene may also experience some bleeding problems, such as heavy periods. There's also the chance that a girl could be born with haemophilia if both parents have the haemophilia gene.
If you have a family history of haemophilia, you can have tests before, during and after pregnancy to determine if your child has the condition. If there's no family history, haemophilia tends to be diagnosed when symptoms appear in childhood.
Read more about diagnosing haemophilia.
Although there's no cure for haemophilia, treatment usually allows a person with the condition to enjoy a good quality of life.
In recent decades, genetically engineered clotting factor medications have been developed to prevent and treat prolonged bleeding.
These medications are given as an injection, the timing of which depends on how severe the condition is. Injections are usually only given in milder cases in response to prolonged bleeding, whereas more severe cases are treated with regular injections to prevent bleeding.
Read more about treating haemophilia.
Your local haemophilia centre
People with haemophilia should register at their local haemophilia centre, as this is a useful source of advice and support.
Find your local haemophilia centre.
Page last reviewed: 04/03/2015
Next review due: 04/03/2017