Haemophilia and The Genes

Haemophilia and the Genes

Haemophilia is not just a single disease, but rather one of a group of inherited genetic bleeding disorders that cause abnormal or exaggerated bleeding and poor blood clotting. Haemophilia A and B are inherited in an X-linked recessive genetic pattern and are therefore much more common in males. Haemophilia A happens in about 1 out of every 5,000 live male births; Haemophilia B in about 1 out of 20,000–30,000.

The Royal Disease

Haemophilia is called the royal disease, as several members of European royal families were affected by this disease — inherited from Queen Victoria of England (1837–1901), who was a Haemophilia B carrier. Her eighth son Leopold contracted Haemophilia B, suffered from frequent haemorrhages, and died of a brain haemorrhage at the early age of 31. Two of Queen Victoria’s daughters, Alice and Beatrice, were carriers and transmitted the disease to the Spanish, German, and Russian royal families.

What Causes Haemophilia?

Haemophilia is caused by a defect in the gene that determines how the body makes clotting factors VIII, IX, or XI. These genes are located on the X chromosome, making haemophilia an X-linked recessive disease. Since the genetic defect is on the X chromosome, fathers cannot pass the disease to their sons. A female who has the altered gene on one of her X chromosomes is called a “carrier” — she may pass the disease to her children but typically does not have the disease herself, though carriers often have an increased risk of bleeding.

Symptoms

• Blood in the urine or stool

• Bleeding gums and frequent nosebleeds

• Large, unexplained bruises and deep bruises

• Excessive bleeding from injuries

• Pain and tight joints

• In severe cases: blurred or doubled vision, extreme sleepiness, continuous bleeding, neck pain

The Role of Genetic Counselling

Genetic testing and genetic counselling for an individual or a child suspected to have haemophilia can help with accurate diagnosis, long-term disease management, predicting risk for at-risk family members, and guiding decisions about prenatal genetic testing or preimplantation genetic diagnosis (PGT).