What Is Myelofibrosis?
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Medically reviewed by Gagandeep Brar, MD
Myelofibrosis (MF) is a rare form of blood cancer that causes scarring (fibrosis) in the bone marrow—the spongy tissue inside your bones that produces blood cells. The scarring disrupts the normal production of blood cells, and some blood-producing cells can move from the bone marrow to the spleen and liver. This leads to a decrease in healthy red blood cells, white blood cells, and platelets.
As a result, people with myelofibrosis often develop anemia and may experience fatigue, easy bruising or bleeding, night sweats, frequent infections, and unexplained weight loss, among other symptoms. Acquired (not inherited) gene mutations cause about 50% of all MF cases. In other cases, underlying blood disorders can lead to the development of the disease.
Between 16,000 to 18,000 people in the United States live with myelofibrosis. Treatment approaches include medications and blood transfusions to manage symptoms and prevent complications. Early studies and interventions also show that a stem cell transplant can potentially cure some people with MF.
Types of Myelofibrosis
There are two types of myelofibrosis: primary and secondary. Though the causes of each type differ, treatment approaches are similar.
Primary Myelofibrosis
Primary myelofibrosis is the most common type and accounts for about 60% of all cases. The condition occurs spontaneously, without an underlying blood or bone marrow disorder or medical condition. Acquired gene mutations cause most cases of primary myelofibrosis, but what causes these gene mutations is unknown.
Secondary Myelofibrosis
Secondary myelofibrosis develops due to an underlying blood or bone marrow disorder—most commonly polycythemia vera (PV) or essential thrombocytosis (ET). PV happens when your body produces too many blood cells (primarily red blood cells). ET is a condition that occurs when your body produces too many platelets. In about 10-20% of people with PV or ET, the condition progresses to myelofibrosis.
Symptoms
Myelofibrosis develops slowly, and most people do not experience symptoms in the early stages of the disease. As fibrosis (scarring) in the bone marrow worsens, the production of normal blood cells slows down. Having too few healthy blood cells leads to symptoms of MF. Common symptoms of this cancer include:
Weakness
Pale skin
Easy bruising or bleeding
Frequent infections
Abdominal pain due to an enlarged spleen (splenomegaly) or enlarged liver (hepatomegaly)
Unintentional weight loss
Itchy skin
Causes
Myelofibrosis develops when mutations (changes) happen in the DNA of your bone marrow stem cells. These mutations cause the stem cells to produce rapidly growing cells, replacing healthy bone marrow with scar tissue. This scarring prevents the bone marrow from producing enough healthy blood cells, leading to a shortage of red blood cells, white blood cells, and platelets.
Gene mutations lead to the development of myelofibrosis. These gene mutations are acquired—meaning you don't inherit a gene mutation from your parents. The cause of these gene mutations is currently unknown. Researchers have discovered a connection between certain gene mutations and the development of myelofibrosis. About 90% of people with myelofibrosis have gene mutations in one or more of the following genes:
JAK2 gene: About 60% of people with primary MF have a mutation in the Janus kinase-2 gene (JAK2). This gene helps signal cell growth and division and plays a crucial role in controlling the production of blood cells. Mutations in the JAK2 gene cause an overproduction of abnormal bone marrow cells, leading to scar tissue formation in bone marrow.
CALR gene: Up to 35% of people with primary MF have a calreticulin (CALR) gene mutation. This gene provides instructions for producing calreticulin, a protein that's involved in several cell functions. Researchers are currently working to understand the mechanisms behind this gene mutation and the development of primary MF.
MPL gene: The MPL gene, found in about 5-8% of those with MF, gives your body instructions for making a protein that promotes the growth and division of platelets. Mutations in the MPL gene cause abnormal cells to release collagen, which usually provides structural support for bone marrow cells but instead causes scar formation in MF.
People with primary MF often have three or more gene mutations associated with the disease, and people with secondary MF may have only one gene mutation. However, people with secondary MF also have an underlying blood or bone marrow disorder contributing to the development of the disease.
Risk Factors
The risk factors for developing myelofibrosis include:
Age: Myelofibrosis tends to be more common in people over 60, though it can also affect children and young people.
Chemical exposure: Exposure to benzene and toluene (chemicals found in gasoline and other industrial products) and radiation increases the risk of myelofibrosis.
Other blood disorders: People with certain other blood disorders, such as polycythemia vera or essential thrombocythemia, are at an increased risk of developing secondary myelofibrosis.
Diagnosis
Diagnosing myelofibrosis involves a physical examination, medical history and symptom review, and diagnostic tests.
Your healthcare provider will begin by asking about your symptoms, medical history, and family history. They will also want to know what medications you are taking. During the physical examination, your healthcare provider will listen to your heart and lungs and feel your stomach to determine if you have an enlarged spleen or liver, which can be a sign of myelofibrosis.
They will also order diagnostic tests to rule out other conditions and confirm a myelofibrosis diagnosis. These tests may include:
Complete blood count (CBC) with differential: A CBC measures the number of red blood cells, white blood cells, platelets, and iron-rich proteins in the blood. People with MF often have low levels of red blood cells, and some have abnormally high or low numbers of white blood cells and platelets.
Peripheral blood smear: A peripheral blood smear is a microscopic examination of a blood sample. This test helps identify abnormal blood cells, which are often tear-dropped shaped in people with MF. People with MF may also have immature blood cells (blasts) in their blood, which does not occur in people without this cancer.
Bone marrow aspiration and biopsy: If your blood tests show that you may have MF, your healthcare provider will order a bone marrow biopsy. A bone marrow biopsy uses a needle to remove a sample of liquid bone marrow from your hip. Then, they send your sample to a lab and study the cells under a microscope to identify scar tissue and abnormal blood cells in the bone marrow.
Genetic testing: Involves taking a blood or cheek swab sample to identify mutations associated with MF, such as mutations in the JAK2, CALR, or MPL genes.
Imaging tests: Ultrasound scans can measure the spleen and magnetic resonance imaging (MRI) can help identify scarring in the bone marrow.
Treatment
Your exact treatment options for myelofibrosis will depend on the severity of your symptoms. People with MF who are symptom-free don't usually require treatment. They will see their healthcare provider frequently to monitor whether the disease has progressed and if treatment is needed.
If you require treatment, interventions for MF help control symptoms and prevent complications. Treatment may include a stem cell transplant, blood transfusions, and medications.
Stem Cell Transplant
The only potential treatment that can cure myelofibrosis is allogeneic stem cell transplantation (ASCT). ASCT is a procedure that involves transplanting stem cells from a healthy donor into your body. The donor's healthy stem cells will replace your stem cells and stimulate the production of healthy blood cells.
ASCT is a risky procedure with serious side effects, so it is typically only considered for younger people with severe myelofibrosis who are otherwise healthy. Older adults or those with other health conditions may not be good candidates for ASCT. They may qualify for reduced-intensity or "nonmyeloablative" allogeneic stem cell transplantation, which involves lower doses of chemotherapy drugs or radiation in preparation for the transplant.
Blood Transfusions
Many people with MF have moderate to severe anemia symptoms due to a lower-than-normal amount of red blood cells. Blood transfusions boost your red blood cell count to relieve anemia symptoms, such as fatigue, shortness of breath, and weakness. People with MF may require blood transfusions every one to three months, depending on the severity of anemia.
JAK Inhibitors
JAK inhibitors are medications that block the activity of the JAK2 protein and inhibit the growth and division of abnormal blood cells. JAK inhibitors help slow the rate of fibrosis, decrease the size of your spleen, and reduce symptoms like night sweats, itching, and bone pain. Your healthcare provider may prescribe you Jakafi (ruxolitinib), Inrebic (fedratinib), or VONJO (pacritinib).
Supportive Care
Treatments that help manage specific symptoms include:
Splenectomy: Surgical removal of the spleen may help people with an enlarged spleen that may be causing severe symptoms, such as abdominal pain and loss of appetite.
Myelosuppressive agents: Hydrea (hydroxyurea) and Busulfex (busulfan) may reduce abnormally high white blood cell and platelet counts and help shrink an unusually large spleen.
Androgen therapy: Synthetic male hormones (known as androgens), such as Danocrine (danazol), may help boost red blood cell production and improve anemia symptoms.
The treatment of myelofibrosis is an evolving field, and researchers are still developing new drugs and therapies to help manage symptoms and improve the quality of life of people with MF. Clinical trials help researchers determine the effectiveness of new treatments. Talk to your healthcare provider if you want to participate in a clinical trial.
How to Prevent Myelofibrosis
Unfortunately, there is currently no known way to prevent myelofibrosis. Regular checkups with your healthcare provider can help identify and treat myelofibrosis early to manage symptoms.
Related Conditions
People with myelofibrosis may have an increased likelihood of developing the following related conditions:
Portal hypertension: An enlarged spleen increases blood flow and raises blood pressure in the vein that carries blood from the spleen to the liver (called the portal vein). This can lead to excess blood leaking into smaller veins in the stomach and esophagus, causing them to rupture and bleed.
Acute myeloid leukemia (AML): An aggressive blood cancer that develops in the bone marrow. Between 10% to 20% of people with MF will eventually develop AML.
Extramedullary hematopoiesis: When the bone marrow doesn't produce enough blood cells, they may form outside the bone marrow, creating clumps (tumors) of developing blood cells throughout the body. These tumors can cause gastrointestinal bleeding, spinal cord compression, or seizures.
Living With Myelofibrosis
Living with myelofibrosis involves following your treatment plan and adapting to potential changes in your health over time. The prognosis for myelofibrosis varies widely from person to person, ranging from two years to over 20 years after diagnosis, with a median survival rate of 6 years. Thanks to research advancements in treatments, including targeted therapies and stem cell transplantation, survival rates have increased significantly in recent years.
It is important to take care of yourself both physically and emotionally when you are living with myelofibrosis. This includes regular checkups with your healthcare provider, finding sources of strength and support (such as through family and friends), and finding healthy ways to cope with your diagnosis, such as by joining a support group or seeing a mental health professional.
Frequently Asked Questions
What is the life expectancy of myelofibrosis?
Your life expectancy with myelofibrosis depends on the severity of the disease and your overall health. However, with proper treatment and management, most people with myelofibrosis can live long and fulfilling lives. The median survival rate for people with myelofibrosis is currently about six years.
Is myelofibrosis curable?
The only potential treatment that may be able to cure MF is a stem cell transplant. This procedure can be risky and has serious side effects. Not everyone with MF is a good candidate for the procedure, but if you're interested in a stem cell transplant, talk to your provider to see if this treatment is right for you.
How aggressive is myelofibrosis?
Myelofibrosis is a rare form of blood cancer that can be aggressive or slow-growing. The rate at which myelofibrosis progresses varies from person to person. Some people with myelofibrosis may experience symptoms for many years before the disease progresses to a more advanced stage. In up to 20% of people, MF progresses to acute myeloid leukemia (AML)—a more aggressive form of blood cancer.
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