What is haemophilia A?
Knowing what haemophilia A is, the right care for it, and learning how to manage the risks of bleeding and joint pain may help you to take control of your health. With the right approach, you can potentially reduce the impact of these challenges and maintain an active, fulfilling lifestyle.
What is haemophilia A?
Haemophilia is a rare bleeding disorder where the ability of blood to clot is reduced.1 Haemophilia A is the most common type of haemophilia.1 It is caused by a genetic mutation that affects the production of clotting factors.1,2 In haemophilia A, the missing clotting factor is factor VIII.1,2
Haemophilia A is more common in males, affecting approximately 1 in 5,000 newborn males.1,2 It affects all races and ethnicities equally.1
The severity of haemophilia A can vary depending on the factor VIII levels in the blood.1,2 There are three levels of severity:1,2
- Mild: Factor VIII levels between 5%–40% of normal
- Moderate: Factor VIII levels between 1%–5% of normal
- Severe: Factor VIII levels below 1% of normal
Approximately 60% of those affected have the severe form of haemophilia A.1
The most common symptom of haemophilia A is excessive bleeding into muscles and joints.3,4 External bleeding from cuts and injuries can also occur.4
How does blood clotting work?
Image 1. What happens when there is a damage to a blood vessel
Blood vessels carry blood to the muscles and tissues surrounding joints.5,6 Clotting factors, including FVIII in haemophilia A and factor IX in haemophilia B, are present within the blood.5,6 When a blood vessel is damaged, blood can escape – known as a bleed. 5,6 This starts a process involving clotting factors and specialised blood cells called platelets. 5,6 Platelets block the site of injury while the clotting process takes place. 5,6
In haemophilia A, missing or defective clotting factors prevent the natural clotting process of creating a blood clot. This can result in the site bleeding for longer and injured blood vessels cannot heal as normal.7
What is a joint bleed?
Image 2. What happens during a joint bleed.
Joint bleeds are one of the most common and debilitating complications of haemophilia A.8
Spontaneous bleeds are sudden bleeds that cannot be attributed to an obvious injury and occur more frequently with severe haemophilia A.3,8,9
In people with haemophilia A, blood can leak into joints such as the knees, elbows, or ankles.3,8,9
Over time, repeated joint bleeds can lead to:8
- Tissue damage, where the soft tissue inside the joint, including cartilage and ligaments, can become damaged
- Muscle weakness can occur if joints become swollen or painful
- Bone deterioration, causing deformities and long-term damage
- This can cause loss of movement and constant, severe, chronic pain, impacting your ability to carry out day-to-day activities and your quality of life
Joint bleeds should be treated quickly to reduce the pain and to try to prevent further joint damage.3,8
How is haemophilia A treated?
The aim of haemophilia A treatment is to prevent and manage bleeding episodes.3
Factor replacement therapies are the most commonly used for the treatment of haemophilia A and aim to replace the missing factor VIII in the blood.3
Prophylaxis
Prophylactic treatment can involve factor replacement therapy and non-factor replacement therapies.3 Factor therapy works by replacing the missing or deficient factor VIII (the protein crucial for blood clotting) helping the blood to clot and can minimize the likelihood of bleeds10. Non-factor therapies work by mimicking the function of missing factor VIII in the blood clotting cascade - rather than directly replacing it - to prevent or reduce a bleed.11
Monitoring the amount of factor VIII in the blood can help to understand the protection level during prophylactic treatment; however, other factors are also important for personalizing treatment.3
Tailoring haemophilia A treatment
Since each individual’s needs and lifestyle are unique, treatment for haemophilia A should be tailored for each person by their healthcare team.3 Factors such as age, physical activity levels, lifestyle, number of bleeds and joint status.3
On-demand treatment
Unlike prophylaxis, on-demand treatment consists of factor replacement therapy in response to a bleed rather than regular treatment to prevent bleeds.3
Emerging treatments for haemophilia A
Gene therapy for haemophilia requires the introduction of a functioning gene into the liver cells, enabling your body to produce its clotting factor.12 Research is ongoing into other treatment options for haemophilia A.12 These include treatments that aim to prevent bleeds without replacing the missing clotting factor. 13 Some rebalancing agents are already available.
Although haemophilia A affects the blood’s ability to clot and may impact joint and muscle health, with proper management, it is possible to achieve your personal goals and live a healthy, active life.
- National Organization for Rare Disorders (NORD). Hemophilia A. Available at: https://rarediseases.org/rare-diseases/hemophilia-a/. Accessed February 2025.
- Castaman G and Matino D. Haematologica 2019;104(9):2–9
- Srivastava A, Santagostino E, Dougall A, Kitchen S, Sutherland M, Pipe SW, et al. Haemophilia 2020;26(6):1–158.
- The Haemophilia Society. Understanding haemophilia booklet. Available at: https://haemophilia.org.uk/wp-content/uploads/2017/04/Understanding_haemophilia_WEB.pdf. Accessed February 2025.
- WFH e-learning. Inherited bleeding disorders. Available at: https://elearning.wfh.org/elearning-centres/inherited-bleeding-disorders/#clotting_process (last accessed February 2025)
- The Haemophilia Society. Rare bleeding disorders. Available at: https://haemophilia.org.uk/wp-content/uploads/2023/07/THS_A5_RareDiseases_JC_website.pdf. Accessed February 2025.
- Great Ormond Street Hospital for Children. NHS Foundation Trust. Haemophilia A. Available at: https://www.gosh.nhs.uk/conditions-and-treatments/conditions-we-treat/haemophilia-0/. Accessed April 2025.
- Knobe K and Berntorp E. J Comorb 2011;1:51–59.
- WFH e-learning. Hemophilia. Available at: https://elearning.wfh.org/elearning-centres/hemophilia/. Accessed February 2025.
- World Federation of Hemophilia. Clotting factor replacement therpaies. Available at: https://www1.wfh.org/publications/files/pdf-2365.pdf Accessed April 2025.
- The Haemophilia Society. Non-factor replacement therapies. Available at: https://haemophilia.org.uk/bleeding-disorders/treatment-types/non-factor-replacement-therapies/ Accessed April 2025.
- The Haemophilia Society. Understanding gene therapy for haemophilia. Available at: https://haemophilia.org.uk/wp-content/uploads/2024/10/Gene-Therapy_A5_THS_V7-1.pdf Accessed April 2025.
- Iurea I-M, Severin E, Matei A. Life (Basel) 2024;14(12):1568.
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