Haemophilia describes a group of inherited blood disorders in which there is a life-long defect in the clotting mechanism of the blood. Blood contains many proteins called clotting factors, and these work to stop bleeding. The lack of clotting factor causes people with haemophilia to bleed for longer periods of time, than people whose blood factor levels are normal.

Figure 1: The normal clotting process

Figure 2: The clotting process in a person with haemophilia, where a clotting factor is missing.

Many people think that people with haemophilia bleed a lot from minor cuts. In reality, external cuts, wounds, or bruises are usually not serious. Most bleeding in haemophilia occurs internally, into the joints or muscles. The joints that are most often affected are the knee, ankle and elbow. Repeated bleeding without prompt treatment can result in long term damage to the joint or muscle. When bleeding occurs in a vital organ, especially the brain, this can be very serious.

Haemophilia is a genetic blood disorder, which is usually inherited. The gene is passed down from a parent to a child (see more). A person who is born with haemophilia will have it for life. Some of the signs of haemophilia are: large or frequent bruising, bleeding into muscles and joints, spontaneous bleeding and bleeding for a long time after a cut or surgery. In women, menstrual bleeding can also be a significant symptom.
There are two types of haemophilia:
Haemophilia A which is a deficiency in factor VIII. The incidence of haemophilia in the general population is 1 in 10,000.
Haemophilia B (sometimes called Christmas Disease) is a deficiency in factor IX. This is a less common form and has an incidence of haemophilia in the general population is 1 in 30,000.
Types of Haemophilia

Severity of haemophilia Percentage of normal factor activity in blood Number of international units (IU) per millilitre (ml) of whole blood
Normal range 50%-150% 0.50–1.5 IU
mild haemophilia 5%-40% 0.05–0.40 IU
moderate haemophilia 1%-5% 0.01¬–0.05 IU
severe haemophilia less than 1% less than 0.01 IU

People with severe haemophilia have less than 1% of the normal level of factor VIII or IX in the blood. This means there is no clotting factor to respond to bleeding. Without treatment, people with severe haemophilia can bleed several times a month. The bleeding is often the result of a minor injury such as a bump or twist. Sometimes, there is no apparent cause for the bleeding. Treatment taken regularly(prophylaxis), in the form of intravenous (into a vein) or subcutaneous (under the skin) aims to minimise how often these happen. Almost all people severe haemophilia receive prophylaxis.
Those with moderate haemophilia can bleed less often as they have a small amount of clotting factor, and this is offers some protection from bleeding. These usually happen more often after minor trauma, such as a sports injury. Like severe patients, treatment taken regularly prevents or reduces damage occurring and most people receive prophylaxis regularly.
Those who have mild haemophilia generally only experience bleeding problems after an obvious injury or an operation and many mild cases have only been after, for example, a tooth extraction or surgery. About 5-10% of those with mild haemophilia receive prophylaxis in the same way as those with moderate or severe. As there is some level of factor already in the body, other types of treatments can be used