Posted On May 07, 2020
4 min read
Hemophilia is a rare inherited condition that affects the blood's ability to clot. People having haemophilia usually experience prolonged bleeding or oozing following an injury, surgery or having a tooth extracted. People with haemophilia lack certain proteins in their blood called clotting factor which play an important role in controlling bleeds. There are two types -Haemophilia A (clotting factor VIII deficiency) and Haemophilia B (factor IX deficiency).
Haemophilia occurs more commonly in males than in females. It is found in all races and socioeconomic groups across the globe. Haemophilia A is more common and occurs in about 1 in 5,000 births and the less common Haemophilia B occurs in 1 in about 20,000 births.
Depending on the level of clotting factor present, the severity of the condition can range from mild (> 5% - 40% of factor VIII or IX), moderate (1-5% of factor VIII or IX) to severe (<1% of factor VIII or IX). Patients with severe haemophilia can bleed spontaneously, without any injury, while mild haemophilia patients will bleed only after injury or surgery.
People with haemophilia may have:
nosebleeds that take a long time to stop
bleeding from wounds that last a long time
skin that bruises easily
pain and stiffness around joints, such as elbows, because of bleeding inside the body (internal bleeding)
Haemophilia is caused by mutations, alteration in genetic material, in the genes F8 and F9 causing haemophilia A and haemophilia B respectively. The mutations in the F8 or F9 gene causes the deficiency of the clotting factors and the altered protein produced cannot participate effectively in the blood clotting process and results in prolonged periods of bleeding.
Haemophilia A and B are inherited in an X-linked recessive manner. The genes F8 and F9 are located on the X chromosome. Males have one X chromosome and one Y chromosome. Hence one altered copy of the gene is enough to cause the disease. Females have two X chromosomes and mutation would have to occur in both copies of the gene for her to be affected (which is very unlikely). Hence males are more likely to be affected than females.
If a female has a mutation in one copy of the gene, she is said to be a carrier, i.e. she remains unaffected and can pass on this mutated gene to future generations. The sons who inherit the abnormal gene will be affected and the daughters will be carriers.
Affected males transmit the pathogenic variant to all their daughters (who will only be carriers) and none of their sons.
However, about 10 per cent of carrier females have less than half the normal amount of one of these clotting factors and are at risk for bleeding.
In nearly 30% of cases of haemophilia, there is no known family history of haemophilia and it happens due to a new mutation in the genes.
There are blood tests available to check the clotting activity of factor VIII and XI. If there's no family history of haemophilia, it's usually diagnosed when a child begins to walk or crawl. In mild haemophilia, it may only be discovered later, usually after an injury or a dental or surgical procedure. Visit Manipal, the best genetics hospital in Bangalore for the diagnosis of Haemophilia.
If you have a family history of haemophilia and you're planning to get pregnant, it’s important to do genetic tests to establish a molecular diagnosis that can help you find out the risk of passing the condition on to a child.
Prenatal diagnosis, tests during pregnancy can diagnose haemophilia in the baby. In this, chorionic villus sampling (CVS), a small sample of the placenta is removed from the womb and tested for the haemophilia gene, usually during weeks 12 to 14 of pregnancy. As it’s an invasive procedure, there's a small risk of miscarriage. Consult with a genetics doctor in Bangalore to know more about Haemophilia.
With factor replacement therapy, most people with haemophilia can live a normal life.
However, they should avoid:
activities that involve a high risk of trauma like contact sports
medicines that can affect your blood's ability to clot, such as aspirin and ibuprofen
circumcision of at-risk males
Head of Department & Consultant, Medical Genetics