Haemophilia is a bleeding disorder whereby blood doesnt clot properly.

Treatment involves injecting the factor required so blood can clot normally. A person with haemophilia does not bleed any faster than a person without haemophilia, but the bleeding continues for longer if it is not treated. Internal bleeding (often referred to as a ‘bleed’) is the biggest problem for people with haemophilia.

Haemophilia is caused be a sex-linked recessive gene therefore in order for it to be expressed in the phenotype it must be homozygous. Every person has two sex chromosomes. Women have two X-chromosomes while a man has one X and one Y chromosome. Both factor VIII and IX proteins are located on the X chromosome. A fault in the Factor VIII or IX gene on the X chromosome will result in Haemophilia A or B. Therefore a woman can be normal, a carrier or haemophilia positive, however males can be haemophilia positive or negative because there is not a normal X chromosome to balance the abnormality, and for this reason men are more prone to inheriting haemophilia. In females carrying the haemophilia gene, the normal X chromosome compensates for the abnormal X chromosome.

An affected male cannot pass the disorder on to his sons but all his daughters will carry the haemophilia gene. Although females only rarely have symptoms of the disorder, they may carry the haemophilia gene and may pass on the disorder to their sons. Sons of women with the haemophilia gene have a one in two chance of being affected and daughters will have a one in two chance of carrying the haemophilia gene.

Though there is no cure for haemophilia, it can be controlled with regular injections of the deficient clotting factor, i.e.  in haemophilia A or  in haemophilia B. Some haemophiliacs develop antibodies (inhibitors) against the replacement factors given to them, so the amount of the factor has to be increased or non-human replacement products must be given.