An inherited disorder of blood COAGULATION which results in prolonged bleeding even after minor injury. There is a deﬁciency of factor VIII, an essential clotting factor in the coagulation cascade – the complex series of biochemical events that leads from injury of the wall of a blood vessel to the formation of a blood clot that checks bleeding. Haemophilia is a sex-linked recessive disorder (though a small number of cases arise by spontaneous mutation), so that, if females carry the disease, one-half of their sons will be aﬀected and one-half of their daughters will be carriers. The sons of haemophiliacs are unaﬀected but one-half of their daughters will be carriers.
Haemophilia aﬀects approximately 1:4,000 of the UK population but only 1:20,000 is severely aﬀected. Severity of the disease depends upon the percentage, compared with normal, of factor VIII activity present. Less than 1 per cent and there will be spontaneous bleeding into joints and muscles; 1–5 per cent and there will be occasional spontaneous bleeding and severe bleeding after minor injury; 5–25 per cent and there will only be severe bleeding after major injury. Before treatment was available, severe haemophiliacs suﬀered from acute pain and deformity from bleeds into joints and muscles. Bleeding also occurred into the gut, kidneys and brain, and few survived past adolescence.
Freeze-dried factor VIII may be kept in domestic refrigerators. Haemophiliacs can use it to abort minor bleeds by reconstituting it and injecting it intravenously. More major bleeding or preparation for surgery involves raising factor VIII levels to 30–100 per cent by giving cryoprecipitate.
With treatment, most haemophiliacs lead normal lives, although obviously dangerous or contact sports should be avoided. Before donors of blood were screened for HEPATITIS B and C or for HIV infection (see AIDS/HIV), some individuals with haemophilia receiving factor VIII were unwittingly infected with those diseases. Today’s screening procedures make such infections very unlikely.
There is a National Haemophilia Register and each registered suﬀerer carries a card with details about his or her condition. Information may also be obtained from NHS haemophilia centres and the Haemophilia Society.