What are haemophilia A & B?
- Haemophilia A is more common than haemophilia B, affecting one in 5,000 males compared to one in 40,000 males.
- Both haemophilia A and B are disorders caused by mutations on genes on the X chromosome (X-linked disorders).
- Queen Victoria was a carrier of haemophilia A.
- Haemophilia A and B are both recessive conditions, which means that someone has to have two mutated copies of the gene to display symptoms (with just one mutated copy they are a carrier).
- However, because the mutated gene is on the X chromosome, it is much more common for males to be affected than females because males only have one X chromosome.
- The disease genes are called F8 and F9 and are found close together on the X chromosome.
- A mutation in the F8 gene results in haemophilia A and a mutation in the F9 gene results in haemophilia B.
- The F8 and F9 genes code for the proteins Factor VIII and Factor IX respectively.
- Factor VIII and Factor IX are coagulation factors that each have an important role in the blood clotting process.
- A mutation in either the F8 gene or F9 gene can result in abnormal or reduced amounts of Factor VIII and Factor IX.
- In cases of severe haemophilia the activity of these factors can be lost altogether.
- Without these factors, the blood clotting process does not work as efficiently and blood clots cannot form properly in response to injury.
- The result is continuous bleeding that can be difficult to control, leading to extensive blood loss.
- The symptoms of haemophilia are easily recognisable as bleeding, haemorrhaging and bruising.
- Haemophilia A and B have very similar symptoms that can range from mild to very severe depending on how much the levels of Factor VIII and IX are affected.
- Healing after trauma or surgery often takes a lot longer in patients with haemophilia.
- Delays in clotting can cause internal bleeding that result in swelling and pain in the joints.
- Physicians can determine whether a patient has haemophilia A or B by seeing whether symptoms are reduced by prescribing Factor VIII or IX.
- If Factor VIII relieves the symptoms of the disease the patient has haemophilia A, if Factor IX does it is haemophilia B.
- Genetic testing can also be used to identify whether the F8 or F9 gene is mutated, and therefore whether the person has haemophilia A or B.
- Regular injections of Factor VIII or Factor IX into the blood are used to manage haemophilia A or B respectively.
- Additional injection of clotting factors may be required in situations where bleeding may occur, for example, during surgery.
- Gene therapy is being investigated as a potential treatment option.
- One study at University College London has looked at injecting haemophilia B patients with a virus containing a section of DNA carrying the instructions for making normal Factor IX.
- Levels of Factor IX in the blood of those injected with the virus rose for the 16 months of the study. As a result some of the patients no longer needed to continue their routine Factor IX injections.
- Although a promising result, this technique will need to be tested on a much larger number of patients before the benefits and risks can be properly assessed.
This page was last updated on 2021-07-21
How helpful was this page?👎 👍 Send
What's the main reason for your rating?Send
Which of these best describes your occupation?Send
how old are students / how old are you?Send
What is the first part of your school's postcode?Send
How has the site influenced you (or others)?Send
Thankyou, we value your feedback!
If you have any other comments or suggestions, please let us know at firstname.lastname@example.org
Can you spare 5-8 minutes to tell us what you think of this website? Open survey