Myelofibrosis (MF) is a rare blood cancer where scar tissue forms in your bone marrow. It’s a type of myeloproliferative neoplasm, which means that your body makes too many abnormal blood cells. These cells can replace normal cells. Treatment goals mainly involve managing symptoms and conditions that arise, including anemia and an enlarged spleen.
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Myelofibrosis (MF) is a blood cancer where scar tissue builds up in your bone marrow. This reduces its ability to make blood cells. Bone marrow is the soft, spongy tissue inside your bones. It makes stem cells that mature into red blood cells, white blood cells or platelets.
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With MF, a change in the stem cell’s genes causes it to become a cancer cell that multiplies fast. The cancer causes inflammation that creates scar tissue. The damage makes it harder for your bone marrow to make healthy blood cells. Meanwhile, your spleen (which filters abnormal blood cells) becomes overworked. It can enlarge and cause symptoms.
Myelofibrosis (pronounced “my-low-fi-BRO-sus”) is a lifelong condition that often progresses slowly. But sometimes, it gets worse fast. In some cases, it transforms into an aggressive type of acute leukemia. This is why your healthcare provider will manage your care closely once you’re diagnosed.
There are two types of myelofibrosis:
Myelofibrosis often gets worse slowly. You may not have symptoms for years. When symptoms do start, the first to show are usually severe fatigue (a sign of anemia) and an enlarged spleen. An enlarged spleen may feel like heaviness in your upper left abdomen. Or the area may hurt.
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Other signs and symptoms include:
Primary myelofibrosis happens when the earliest form of a blood cell — a stem cell — transforms into a cancer cell. The cell makes malignant copies (clones) that build up in your bone marrow.
The clones crowd out healthy blood cells. They also release substances that damage your bone marrow. The damage leads to scarring inside your bones.
Doctors don’t know what causes this process in the first place. But they do know that many people with MF have common genetic mutations. A mutation is a change in a gene. The most common ones are:
You may be at increased risk of myelofibrosis if:
As myelofibrosis advances, it can lead to:
Your healthcare provider will do a physical exam and review your medical history. They’ll ask about your symptoms. Tests you may need include:
As part of your diagnosis, your healthcare provider may stage MF as either prefibrotic (early) or overt (advanced). Prefibrotic MF involves less scarring in your bone marrow than overt MF.
Your provider may also score your MF. Scoring systems for MF consider your symptoms, test results and the type of mutation. The results range from low- to intermediate- to high-risk. This helps providers estimate your life expectancy after treatment.
Low-risk MF typically requires less-intensive treatments than high-risk MF.
You don’t need treatment if you have low-risk MF and aren’t symptomatic. Instead, your healthcare provider will monitor you.
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Common medications used to treat intermediate- and high-risk myelofibrosis include JAK inhibitors like:
For most people, the goal of treatment is to manage conditions that cause symptoms. Treatment may also slow disease progression.
Treatments that manage anemia include:
Treatments for an enlarged spleen include:
A hematopoietic stem cell transplant (HCT) is a potential cure for MF. For some people, it’s not a cure, but it helps them live longer. Still, an HCT is a risky procedure with potentially fatal complications. It’s not an option for everyone. Instead, healthcare providers recommend it for people who are diagnosed as high risk.
This procedure involves replacing abnormal stem cells with healthy cells from a donor.
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Your provider will monitor you regularly. In the meantime, let them know what symptoms you’re experiencing. Report any treatment-related side effects you have.
People with more advanced scarring in their bone marrow live about three to seven years after diagnosis. People with prefibrotic (early) MF live for about 10 to 15 years. About 20 out of every 100 people with primary MF develop acute myeloid leukemia within 10 years of their diagnosis.
But it’s important to remember that your prognosis (outlook) depends on lots of things. Your stage, risk score, the type of genetic mutations you have — they’re just some of the factors that matter.
Ask your provider about what your diagnosis means for your experience of the disease.
Ask your healthcare provider if you could benefit from palliative care. Palliative care specialists can help you navigate the challenges of a cancer diagnosis. Unlike hospice care, these providers can help people with chronic illnesses, no matter their prognosis.
You can also ask your provider if you’re a candidate for a clinical trial. Clinical trials study the safety and effectiveness of new treatments. Doctors continue to discover new therapies that are improving the lives of people with MF.
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No two experiences of myelofibrosis (MF) are the same. Depending on your situation, you may go several years with no symptoms. Or symptoms may progress fast, and you find yourself suddenly adjusting to new medications. Regardless, an MF diagnosis requires collaboration with your caregivers. Let your healthcare provider know the symptoms you’re experiencing. Report any side effects from treatment. This may be a chronic condition, but there are treatments that can improve your experience of this disease.
If you have a rare blood cancer like myelofibrosis, you want experts by your side. At Cleveland Clinic, we’re with you from testing to treatment and beyond.
Last reviewed on 06/27/2025.
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