It is a genetic disease that is seen affecting the males in a family. The defective gene in the male causes a deficiency of clotting factor (which is required for normal clotting after bleeding). The disease can be caused by either deficiency of factor VIII (called Haemophilia A, occurs in 85% of cases) or factor IX (called Haemophilia B, occurs in 15% of cases).
Let’s understand the genetic inheritance by understanding various scenarios:
1. If the father has haemophilia but the mother does not, the sons will not have haemophilia. All of the daughters will become carriers of the gene.
2. If the mother is a ‘carrier’ of the defective haemophilia gene but the father is healthy, there is a 50:50 chance of a son suffering from haemophilia or the daughter being a carrier.
3. If the father has haemophilia and the mother is a carrier, the woman will suffer from haemophilia too. However, this is very rare.
Images courtesy: Haemophilia Federation India