What Is Haemophilia B?

Haemophilia B is a rare condition where your blood doesn't clot properly. This happens because your body doesn't have enough of a certain protein called factor IX.¹ This protein helps your blood to stop bleeding when you get a cut or bruise. People with haemophilia  experience prolonged bleeding after injuries or surgeries, and they are also at risk of spontaneous bleeding into their joints, muscles, and other internal organs.¹

Haemophilia B, also known as Christmas disease, is one of the two main types of haemophilia, the other being Haemophilia A. The key distinction between the two lies in the deficient clotting factor. In Hemophilia B, the deficiency is in ‘Clotting Factor IX’ and individuals diagnosed with Haemophilia A commonly suffer from ‘Factor VIII’ deficiency.¹ Haemophilia B  is caused by mutations in the F9 gene located on the X chromosome. As Hemophilia B follows an X-linked recessive pattern of inheritance, it mainly affects males, while females typically carry the gene mutation without experiencing the full-blown disorder themselves.¹

Causes 

Haemophilia B is an inherited bleeding disorder.² If you are diagnosed with haemophilia B, it indicates that you've inherited an atypical/mutated gene impacting the quantity of ‘Clotting Factor IX’ within your blood. Generally, a gene known as F9 (present on the X chromosome) provides your liver with guidance on manufacturing factor IX.⁶ Hemophilia B occurs when this gene undergoes a mutation, resulting in an irregular/abnormal gene that causes diminished levels or even absence of clotting Factor IX. Individuals assigned male at birth inherit haemophilia B when their biological mothers suffer from this condition or carry the mutation for this condition.²

 Here is how it happens:

• Each individual assigned male at birth inherits one X chromosome from their biological mother and one Y chromosome from their biological father.⁷ For individuals assigned female at birth, only two X chromosomes are present, which are inherited from each biological parent.⁷
• In the case of an individual assigned female at birth (DFAB) with a mutated F9 gene on one of their X chromosomes, they are carriers of Haemophilia B but do not exhibit symptoms.⁷ This is due to the presence of a healthy F9 gene on their other X chromosome inherited from the other parent.⁷ However, if both parents possess the mutated F9 gene, then the possibility of an individual assigned female at birth suffering from Haemophilia B is stronger.2,7 But in general populations, this does appear to be a very rare case, with individuals assigned male at birth at much higher risk of suffering from Haemophilia B.⁷
• Furthermore,  carriers have the potential to transmit the X chromosome with the mutated F9 gene to their biological male offspring. Since males or individuals assigned male at birth possess only one X chromosome, they will develop Haemophilia B due to the mutation on that single chromosome.⁷

Symptoms 

Bleeding tendencies:

Common sites of bleeding (joints, muscles, internal organs):

Individuals with Hemophilia B exhibit distinctive bleeding tendencies.³ Bleeding often occurs in specific areas such as joints, muscles, and internal organs.³ Joints are particularly vulnerable, and repeated bleeding into the joints, known as  Haemarthrosis (Haem = blood, Arthosis = Joints), can lead to chronic pain and damage to joints.³ Muscle bleeds can result in swelling and discomfort, while internal organ bleeding might have more subtle symptoms but can be equally serious.³

Severity levels (mild, moderate, severe):

Haemophilia B presents in varying degrees of severity, classified as mild, moderate, or severe, based on the deficiency levels of clotting factor IX in the blood.^1,7

Mild Haemophilia B - experiences minimal bleeding episodes, often only after significant injuries or surgeries that may involve large amounts of blood loss.^1,7 

• Moderate - cases have somewhat reduced factor IX levels, leading to bleeding following minor trauma.
• Severe Haemophilia B -  by significantly low or absent factor IX, results in spontaneous bleeding, sometimes even without apparent cause. In severe cases, internal bleeding is very common and can lead to the formation of haematomas (local blood collection internally) and swellings due to internal bleeding. In some cases, they may also cause obstruction in breathing due to internal bleeding in the tongue.^1,7 Understanding the severity helps guide appropriate treatment and management strategies for each individual.^1,7 

Complications:

Joint damage: One of the significant complications of Haemophilia B is the potential for joint damage.³ Recurrent bleeding into the joints, particularly weight-bearing joints, can cause ongoing inflammation and damage to the joint structures.³ Over time, this can lead to chronic pain, joint deformities, and limited range of motion.³ Managing joint health is crucial to prevent long-term complications and maintain overall mobility.³

Haemarthrosis (bleeding into joints): Haemarthrosis, the bleeding into joints, is a common and concerning complication of Hemophilia B. This condition occurs when blood accumulates within the joint spaces, causing intense pain, swelling, warmth, and limited movement.^1,7 Without prompt and appropriate treatment, hemarthrosis can lead to joint deterioration and disability. Regular factor replacement therapy and preventive measures are essential to reduce the occurrence of hemarthrosis.^1,7

Other health implications: Beyond joint-related issues, Haemophilia B can have additional health implications. Internal bleeding, even if not immediately visible, can occur in vital organs and soft tissues, potentially leading to organ damage or complications.^1,7 Frequent bleeding episodes might necessitate medical interventions, which can introduce risks of infection or other treatment-related complications. Additionally, the emotional and psychological impact of living with a chronic bleeding disorder can affect a person's overall well-being and quality of life, thus highlighting the importance of holistic care and support throughout their treatment is necessary.^1,7

Diagnosis 

Diagnosing Haemophilia B involves a combination of medical history assessment, blood tests to measure clotting factors, and genetic testing to identify the specific F9 genetic mutations.⁴

Medical history and family history:

Diagnosing Haemophilia B often begins with a thorough review of the individual's medical history and a comprehensive understanding of their family history.^1,7 Gathering information about any unusual bleeding tendencies, prolonged bleeding after injuries, surgeries, or dental procedures, and instances of spontaneous internal joint or muscular bleeding can provide valuable insights.^1,7 Family history plays a significant role since  Haemophilia B is a genetic disorder and tends to run in families. If other family members, particularly males, have a history of bleeding disorders, it raises suspicion for Haemophilia B.^1,7

Blood tests to measure clotting factors:

Blood tests are essential to confirm the diagnosis of Hemophilia B. Specifically, these tests measure the levels of clotting factors in the blood, particularly factor IX. A key test is the Partial Thromboplastin Time (PTT), which assesses the blood's ability to clot.^1,7 Individuals with Hemophilia B exhibit prolonged PTT due to the reduced or absent factor IX.^1,7 Additional tests, such as the clotting factor assay, provide more precise measurements of factor IX levels.^1,7 These tests help categorize the severity of the disorder into mild, moderate, or severe.^1,7

Genetic testing for F9 mutations:

The first step to genetic testing in the UK involves referral to a Geneticist, an individual trained in genetic family mapping and testing (NHS). Genetic testing involves analyzing the F9 gene on the X chromosome to identify specific mutations responsible for Haemophilia B.^1,7 This testing confirms the genetic basis of the disorder and can provide valuable information about the specific mutation type and its potential implications.^1,7 Genetic testing is particularly useful in cases where the diagnosis is uncertain or to identify carriers, especially in females. It also aids in family planning and making informed decisions about reproductive options.^1,7

The combination of medical history, family history evaluation, blood tests, and genetic testing forms a comprehensive diagnostic approach for Haemophilia B. This process ensures accurate diagnosis, helps assess the severity of the disorder, and informs treatment decisions and ongoing management strategies. Early diagnosis is crucial for initiating appropriate interventions, preventing complications, and improving the quality of life for individuals with Haemophilia B.

Treatment and management 

It is important to note that since this is an inherited or genetic disorder, there is no cure for it and treatment and management are primarily focused on reducing further complications and improving the quality of life for the individual. 

Replacement therapy:

1. Factor IX concentrates:

Replacement therapy stands as the primary approach to managing Haemophilia B, and it centers on providing the deficient or missing clotting Factor IX. Factor IX concentrates plays a pivotal role in this strategy.^1,7 These concentrates are derived from either human blood plasma or synthesized using genetic engineering techniques.^1,7 They are concentrated forms of factor IX, which is the essential protein required for normal blood clotting. By infusing Factor IX concentrates into the bloodstream, individuals with Hemophilia B can temporarily enhance their clotting ability to mimic normal clotting for some time, effectively minimizing the risk of excessive bleeding and its related complications.^1,7 The administered Factor IX compensates for the deficiency, facilitating proper clot formation and stopping bleeding more efficiently.⁵

• Prophylactic vs. on-demand treatment:

The utilization of Factor IX concentrates involves two distinct treatment approaches: prophylactic and on-demand. Prophylactic treatment involves scheduled and regular infusions of Factor IX concentrates, irrespective of bleeding episodes.^1,7 The goal is to maintain a consistent level of clotting factor in the bloodstream, thus reducing the likelihood of spontaneous bleeding occurrences.^1,7 This approach is particularly beneficial for individuals with severe Haemophilia B as it can prevent joint damage, limit bleeding-related complications, and enhance overall well-being.^1,7 Conversely, on-demand treatment entails administering factor IX concentrates only when bleeding is anticipated or has occurred.^1,7 This approach is often employed by individuals with milder forms of Haemophilia B who experience bleeding less frequently.^1,7 On-demand treatment is suitable for managing bleeding episodes triggered by injuries, surgeries, or other circumstances.^1,7

The central role of replacement therapy, specifically Factor IX concentrates, in managing Haemophilia B underscores its importance in preventing excessive bleeding and maintaining an active lifestyle.^1,7 The decision between prophylactic and on-demand treatment depends on factors like the severity of the disorder, individual bleeding patterns, and lifestyle considerations.^1,7 Effective communication with healthcare providers, regular monitoring of factor levels, and adherence to treatment plans are critical components in ensuring successful management of Haemophilia B and enhancing the overall quality of life for those affected.^1,7

Summary 

Haemophilia B is a genetic bleeding disorder caused by a deficiency in clotting Factor IX due to F9 gene mutations located on the X chromosome. It mainly affects males and leads to distinct bleeding tendencies, more dangerously internal bleeding tendencies into the joints, muscles, and organs.^1,7 The severity varies, causing joint damage, haemarthrosis, and other health issues.^1,7

Raising awareness about Haemophilia B is vital for early diagnosis and informed decisions.^1,7 Diagnosis commonly involves a medical history, blood tests and genetic history as well as testing.^1,7 Being an inherited condition, it cannot be cured, and management is mainly focused on replacement therapy with Factor IX, which concentrates on managing symptoms and improving the quality of life.1,7 Supportive environments, including networks and resources, are important to address mental health challenges that may arise due to the chronicity of the condition.^1,7 Enhanced understanding, advocacy, and community support improve the lives of those with Haemophilia B.^1,7