Clinical features: Haemophilia A is a bleeding disorder characterised by partial or complete deficiency of clotting factor VIII. Affected individuals present with prolonged bleeding from wounds after injuries, surgery and dental extractions. The condition is extremely variable and in severe haemophilia A, spontaneous bleeding into the joints and muscles is the most common symptom. The severity and frequency of the symptoms and the age at diagnosis are directly related to factor VIII clotting activity. All patients and their families with haemophilia A should be assessed at specialist haemophilia treatment centres. Treatment is usually by intravenous replacement of factor VIII, although the frequency of treatment depends upon the severity of the condition. Until the mid 1980?s this was obtained from donated blood, but more than 1000 haemophiliacs in the United Kingdom became infected with HIV or hepatitis C or both, as a result of receiving contaminated blood products. Nowadays, the mainstay of treatment is an artificially produced factor VIII concentrate that has no human or animal derived proteins. This treatment has improved the life expectancy of affected individuals considerably. Up to 10% of carrier females are at risk of bleeding, but their symptoms are usually mild. However, women who are symptomatic carriers should be monitored during pregnancy and particularly for bleeding post-partum.
Incidence: The birth incidence is about 1 in 4,000 liveborn males. The condition is equally common in all countries of the world and in all races.
Inheritance: X-linked recessive.
Gene: Haemophilia A is caused by mutations in the coagulation factor VIII gene on the X-chromosome. More than 800 mutations have been identified, the commonest, a gene inversion, is present in approximately 45% of affected males. DNA testing can identify a mutation in about 98% of individuals with haemophilia A.
Prenatal diagnosis: Yes. Please refer to your local clinical genetics service prior to a pregnancy. This ensures family members are offered appropriate advice and investigations, to confirm whether or not prenatal diagnosis is possible.
Carrier testing: Yes.
UK Support Group: The Haemophilia Society Petersham House 57a Hatton Garden London EC1N 8JG Free helpline 0800 018 6068 Admin 020 7831 1020 Fax 020 7405 4824 Website: www.haemophilia.org.uk
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