How is Hemophilia Inherited

Hemophilia is a hereditary disorder. It is a rare disease found only in 1 among ten thousand people. Males mostly suffer from this disease; but, there may even be rare cases of females suffering from it. Hemophilia is a disorder that prevents clotting of blood (coagulation). A significant symptom is that the patient bleeds profusely.

There are special proteins present in our body that are known as clotting factors. They are factor VIII and factor IX. They help in clotting of the blood when blood vessels rupture. In case of hemophilia, one of these factors is either absent or present in very less amount. Hence, there is no coagulation of blood and lot of bleeding takes place.

Inheritance of Hemophilia

The genes for the clotting factors are located on the X chromosome. Therefore, hemophilia is a 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 hemophilia 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 crisscross pattern of inheritance is observed in hemophilia.

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. She transfers the affected genes to her son. In all, hemophiliac genes are transferred from grandfather to grandson through the daughter.

Inheritance Pattern

• If the mother is carrier and father does not have hemophilia, there is 50% chance for acquiring the disease in sons while daughters will have 50% chance of being carriers.
• If the father is hemophiliac 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 hemophilia, 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 unlikely for both the parents to be hemophiliac.
• Sometimes, even when there are no traces of hemophilia among the ancestors, a person may acquire the disease. This is due to a change, variation or mutation in the genes.

What are the Types of Hemophilia?

Hemophilia is classified into subtypes like, hemophilia A and hemophilia B. In case of hemophilia A, the amount of factor VIII is very less or absent. Whereas, absence or less amount of factor IX causes hemophilia B. Nearly 80% of the hemophiliac patients have factor VIII deficiency, i.e, they suffer from hemophilia A.

Depending on the amount of coagulating factor present in the body, hemophilia is classified into mild, moderate or severe. In case of mild hemophilia, a person bleeds rarely; while, in severe cases, he bleeds frequently. In case of severe hemophilia, the amount of coagulating factor is very low.

What are the Symptoms of Hemophilia?

The symptoms of hemophilia can be seen only after a person suffers from any injury. The form of bleeding can indicate the presence of hemophilia. Look out for the following symptoms

• Frequent nose bleeding is commonly observed.
• Excessive bleeding after any physical injury.
• Excessive bleeding after any surgery.
• Excessive bleeding after any dental procedure like tooth extraction.
• As internal bleeding occurs in joints and muscles, a person may suffer from joint pain.

If such 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 hemophilia can be diagnosed from these tests.

How is Hemophilia Treated?

The only treatment available is Replacement Treatment. The clotting factor that is absent in the blood of hemophiliac 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 hemophiliacs to undergo treatments as soon as possible because excessive bleeding may also result in death. Even though these treatments are expensive, they are effective.