What Is Myelofibrosis?

Overview

Myelofibrosis (MF) is categorised as a form of bone marrow cancer that hinders the body's capacity to generate blood cells. Classified under the group of myeloproliferative neoplasms (MPNs), these conditions disrupt the normal development and functionality of bone marrow cells, leading to the formation of fibrous scar tissue.

MF can manifest as either primary, occurring independently, or secondary, resulting from another underlying condition, often affecting the bone marrow. In some cases, other MPNs can progress to MF. While certain individuals may remain asymptomatic for extended periods, others experience worsening symptoms due to the scarring that develops in their bone marrow. This article will dive into the potential causes, symptoms, and management options for MF. 

Causes and risk factors of myelofibrosis

The exact cause of myelofibrosis remains unknown to scientists, but they have observed a connection between the condition and specific genetic alterations in DNA.¹ As the mutated cells undergo replication and division, they transmit the mutation to newly formed blood cells. Over time, these mutated cells outpace the bone marrow's capacity to generate healthy blood cells. Consequently, an imbalance occurs, leading to insufficient red blood cells and an excess of white blood cells. Additionally, the presence of these abnormal cells leads to the formation of scar tissue and the hardening of the bone marrow, which is typically a soft and spongy tissue. 

The involvement of Janus-associated kinases (JAKs), a group of proteins, has been identified in the development of myelofibrosis. JAKs are responsible for regulating the division and growth of blood cells in the bone marrow through signalling mechanisms. 

Myelofibrosis is a relatively uncommon condition, affecting approximately 1.5 individuals per 100,000 in the UK. Nonetheless, certain factors can elevate the likelihood of developing this condition, including:

• Age: Although myelofibrosis can occur at any age, it is more frequently diagnosed in individuals over the age of 50
• Pre-existing blood disorder: Some individuals with myelofibrosis experience it as a complication of another underlying condition, such as thrombocythaemia or polycythaemia vera
• Exposure to chemicals: Myelofibrosis has been linked to exposure to specific industrial chemicals like toluene and benzene⁴
• Exposure to radiation: Individuals who have been exposed to radioactive materials may have an increased risk of developing myelofibrosis

Signs and symptoms of myelofibrosis

Myelofibrosis typically develops gradually, often with subtle initial signs that may go unnoticed by many individuals.³ However, as the condition advances and begins to disrupt the production of blood cells, various symptoms may emerge, such as: 

• Fatigue
• Bruising more easily
• Bleeding more easily 
• Nose bleeds
• Bleeding gums
• Shortness of breath
• Night sweats
• Bone pain
• Unintentional weight loss
• Pain on the left side, below your ribs

Treatment and management of myelofibrosis

Treatment for myelofibrosis (MF) is tailored to address specific symptoms experienced by patients. Many common MF symptoms are linked to underlying conditions caused by MF, such as anaemia or an enlarged spleen. The treatment options vary based on the symptoms:²

Managing anaemia

• Blood transfusions: Regular transfusions can increase red blood cell counts and alleviate anaemia-related symptoms like fatigue and weakness
• Hormone therapy: In some cases, a synthetic version of the male hormone androgen may stimulate red blood cell production
• Corticosteroids: These may be used alongside androgens to encourage red blood cell production or reduce their destruction
• Prescription medications: Immunomodulatory drugs like thalidomide and lenalidomide may improve blood cell counts and help with spleen enlargement symptoms

Treating enlarged spleen

• Radiation therapy: Targeted radiation beams can reduce spleen size by killing abnormal cells
• Chemotherapy: Certain chemotherapy drugs might shrink the enlarged spleen
• Surgery: In some cases, a splenectomy (spleen removal) may be recommended if other treatments are ineffective

Addressing mutated genes

A drug called ruxolitinib has been approved to treat MF symptoms by targeting specific genetic mutations that may be associated with MF. Clinical trials have shown its effectiveness in reducing spleen enlargement, alleviating MF symptoms, and improving prognosis. 

Experimental treatments

• Stem cell transplant: This procedure has the potential to cure MF and restore bone marrow function. However, it carries significant risks and is typically considered when other treatments fail
• Interferon-alpha: Early treatment with interferon-alfa has shown promise in delaying bone marrow scar tissue formation, but further research is required to ensure its long-term safety 

Diagnosis of myelofibrosis 

Myelofibrosis is typically detected during a routine complete blood count (CBC) test. Individuals with MF commonly exhibit significantly low levels of red blood cells and abnormal counts of white blood cells and platelets. 

Upon reviewing the CBC results, your doctor might conduct a bone marrow biopsy to further investigate the presence of MF. This procedure involves extracting a small sample of bone marrow for closer examination, specifically looking for indications of scarring. 

Additionally, your doctor may recommend an X-ray or MRI scan to eliminate other potential causes of your symptoms or abnormal CBC findings.

Complications

Over time, myelofibrosis can give rise to several complications, which may include:

• Increased liver blood pressure: The enlarged spleen's increased blood flow can elevate pressure in the portal vein of the liver, leading to a condition known as portal hypertension. This can exert excessive pressure on smaller veins in the stomach and oesophagus, potentially resulting in severe bleeding or the rupture of a vein
• Formation of tumours: Blood cells may gather in clusters outside the bone marrow, leading to the growth of tumours in various parts of the body. Depending on the location of these tumours, they can cause different issues, such as seizures, gastrointestinal bleeding, or compression of the spinal cord 
• Risk of acute leukaemia: Approximately 15 to 20 per cent of individuals with myelofibrosis may develop acute myeloid leukaemia, which is a severe and aggressive form of cancer 

Summary

Myelofibrosis is a rare form of bone marrow cancer that disrupts blood cell production and leads to the formation of fibrous scar tissue. It can occur independently (primary) or as a result of another condition (secondary). The condition is associated with specific genetic mutations that affect blood cell development. Myelofibrosis can lead to complications such as increased liver blood pressure (portal hypertension), the formation of tumours in different parts of the body, and a risk of developing acute leukaemia. Treatment options depend on the symptoms experienced, and some experimental treatments are being explored to improve outcomes for patients.