In the human body, each cell contains 23 pairs of chromosomes, one of each pair inherited through the egg from the mother, and the other inherited through the sperm of the father. Of these chromosomes, those that determine sex are X and Y. Females have XX and males have XY. In addition to the information on sex, 'the X chromosomes carry determinants for a number of other features of the body including the levels of factor VIII and factor IX.'1 If the genetic information determining the factor VIII and IX level is defective, haemophilia results. When this happens, the protein factors needed for normal blood clotting are effected. In males, the single X chromosome that is effected cannot compensate for the lack, and hence will show the defect. In females, however, only one of the two chromosomes will be abnormal. (unless she is unlucky enough to inherit haemophilia from both sides of the family, which is rare.)2 The other chromosome is likely to be normal and she can therefore compensate for this defect.
There are two types of haemophilia, haemophilia A and B. Haemophilia A is a hereditary disorder in which bleeding is due to deficiency of the coagulation factor VIII (VIII:C)3. In most of the cases, this coagulant protein is reduced but in a rare amount of cases, this protein is present by immunoassay but defective. Haemophilia A is the most common severe bleeding disorder and approximately 1 in 10,000 males is effected. The most common types of bleeding are into the joints and muscles. Haemophilia is severe if the factor VIII:C levels are less that 1 %, they are moderate if the levels are 1-5% and they are mild if they levels become 5+%.
Those with mild haemophilia bleed only in response to major trauma or surgery. As for the patients with severe haemophilia, they can bleed in response to relatively mild trauma and will bleed spontaneously.
In haemophiliacs, the levels of the factor VIII:C are...
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