World Haemophilia day is observed every year on 17th April to create awareness regarding haemophilia- a rare bleeding disorder. In this article, we will highlight how actually haemophilia is inherited.
Haemophilia is a rare bleeding disorder, found only in 1 among ten thousand people. Usually males suffer from this disease but, there are even rare cases of females suffering from it. Haemophilia is a disorder that prevents clotting of blood (coagulation). Excess bleeding is the most significant symptom of the disease.
There are special proteins present in our body, known as clotting factors that help in clotting of the blood when blood vessels rupture. In case of haemophilia, one of the blood clotting factors (factor VIII and factor IX) is either absent or present in very less amount. Hence, there is no coagulation of blood and excessive bleeding takes place.
Inheritance of Haemophilia
The genes for the clotting factors are located on the X chromosome. Therefore, Haemophilia is an X linked disorder, i.e., it is caused when a defective X chromosome gene is inherited.
Females have two X chromosomes, one inherited from the father and the other from the mother while a male has one X chromosome inherited from the mother and a Y chromosome inherited from the father. Consequently, a direct inheritance of Haemophilia from the father to son is not possible. If a female inherits only one defective X chromosome, she does not suffer from the disorder. However, she will remain a lifelong carrier of the disease and may transfer the defective X chromosome to her male offspring. The probability of a female inheriting two defective X chromosomes is low and so this disease is seen predominantly in males. In this way, a criss-cross pattern of inheritance is observed in haemophilia.
In such type of inheritance, there is no direct transfer of the affected genes from father to son or mother to daughter. Instead, the affected genes are transferred from the father to his daughter. The daughter is not affected by these genes but remains the carrier. The affected genes are transferred to her son. To sum it, haemophiliac genes are transferred from grandfather to grandson through the daughter.
Inheritance Pattern of Haemophilia
What are the Types of Haemophilia?
- If the mother is carrier and father does not have haemophilia, there is 50% chance for acquiring the disease in sons while daughters will have 50% chance of being carriers.
- If the father is haemophiliac while the mother is not, all sons will be normal, but, all daughters will be carriers.
- If the mother is a carrier and father also suffers from haemophilia, sons and daughters, both will have 50% chance of acquiring the disease. Also, daughters have 50% chance of being carriers. However, this case is exceptionally rare as it is very rare for both the parents to be haemophiliac.
- Sometimes, even when there are no traces of Haemophilia among the ancestors, a person may acquire the disease. This is due to a change, variation or mutation in the genes.
Haemophilia is classified into subtypes like, Haemophilia A
and Haemophilia B. In case of Haemophilia A, the amount of factor VIII is very less or absent. Whereas, absence or less amount of factor IX causes Haemophilia B. Nearly 80% of the haemophiliac patients have factor VIII deficiency, i.e., they suffer from Haemophilia A.
Depending on the amount of coagulating factor present in the body, Haemophilia is classified into mild, moderate, or severe. In case of mild haemophilia, a person bleeds rarely while, in severe cases, he bleeds frequently. In case of severe haemophilia
, the amount of coagulating factor is very low.
What are the Symptoms of Haemophilia?
The symptoms of Haemophilia
can be seen only after a person suffers from any injury. The form of bleeding can indicate the presence of haemophilia. Look out for the following symptoms:
If these symptoms are detected, doctors advise the patient to undertake blood tests
like CBC (complete blood count
), VIII factor level, IX factor level, etc. The presence of Haemophilia can be diagnosed from these tests.
How is Haemophilia Treated?
The only treatment available is Replacement Treatment. The clotting factor that is absent in the blood of haemophiliac patients in infused externally through blood transfusion. This has to be done periodically. Once the blood clotting factors are infused in the person's body, they prevent joint damage
. It is advisable for severe haemophiliacs to undergo treatments as soon as possible because excessive bleeding may also result in death. Even though these treatments are expensive, they are effective.