A genetic bleeding disorder caused by lack of blood protein, factor VIII, which is necessary for blood clotting. Haemophiliacs (who are generally always male) suffer recurrent bleeding, often into their joints, which can occur after injury or spontaneously.
Incidence and causes
The deficiency of factor VIII is due to a defective gene, which shows a pattern of sex-linked inheritance. Affected males pass on the gene not to their sons, but to their daughters, who are carriers of the condition. Some of the sons of carrier females can be affected, and some of the daughters of carrier may also be carriers. Most haemophiliacs have a brother, uncle or grandfather who is also affected. However, in roughly one third of cases there is no family history of haemophilia.
The extremity of the disorder differs noticeably among individuals. However, episodes of bleeding are painful and, unless treated immediately, can lead to deformity of the ankles, knees and other joints. Injury, and even small operations such as tooth extraction, can lead to profuse bleeding. Internal bleeding can lead to extensive bruises or blood in the urine.
Haemophilia is diagnosed by amniocentesis, blood clotting tests, or chorionic villus sampling in a foetus. Bleeding can be controlled by infusions of factor VIII concentrates. Those with an extreme form of the disorder can need regular intravenous injections of factor VIII as a preventive measure.
Many people with haemophilia can lead an active normal life but should avoid the risk of injury. Contact sports, such as football, are not recommend, but other forms of exercise, such as swimming and walking, can be beneficial. The female relatives of anyone with haemophilia should have genetic counselling before planning a pregnancy.