Naturally, the body is programmed to be able to stop bleeding by allowing blood to clot whenever there is injury involving breaching of blood vessels. This reduces the quantity of blood loss at the time of injury. However, there are conditions that prevent blood from clotting at the right time, thereby allowing excess blood loss in case of injury or even spontaneous by bleeding into the body spaces like joints, brain, soft tissues of the skin, muscles etc.
One of such conditions preventing blood from clotting is haemophilia. Haemophilia is largely an inherited bleeding disorder which occurs due to deficiency of specific clotting factors. Clotting factors are proteins in the blood that help in blood clotting.
There are thirteen of them labelled factors I to XIII. Those that result in haemophilia when deficient or in low level are factors VIII and IX. The lower the quantity of these factors in the blood, the higher the tendency for abnormal bleeding to occur.
Though haemophilia, being usually an inherited disorder, is present at birth, on rare occasions it can present for the first time later in life i.e. middle age to elderly. Also, the condition occurs more commonly in males (for reasons that will be stated later) but females can also be affected.
Haemophilia results from alteration (mutation) in one of the genes responsible for producing clotting factors. The alteration may result in complete absence or inadequate production of the clotting factors involved, resulting in clotting disorder. The severity of the disorder depends on the degree of alteration in the gene.
This alteration / mutation is usually inherited from parents, although a patient may not have known history if the gene has been carried by females in the family, just by chance or there is a new mutation in the individual.
The genes determining the production of these clotting factors VIII and IX are located on the X chromosome. This is possibly why males are more affected than females because males have only one X chromosome unlike females who have two.
Since many of the genes in X chromosome are not present on Y chromosome, these genes only have one copy, unlike in women where there are two X chromosomes and two copies of the genes, one from each X chromosome. Thus, females are affected when the two X chromosomes are affected by the mutation or one is affected and the other is inactive or not present. When one is affected and the other is active, they are regarded as carriers.
Treatment of haemophilia involves replacement of the missing clotting factor by infusion of the artificially prepared clotting factor concentrates. This is done at every bleeding episode. Regular infusion of this factor concentrate may prevent excessive bleeding at any bleeding episode, thereby serving as prophylaxis.
Prevention of haemophilia is difficult because it is not routinely tested for. It is also not a linearly inherited disorder as new mutation may spring up during development which can make it appear for the first time in a family with no such history.