What Is Myelofibrosis?


Allie Lemco Toren

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When you think of leukemia, you may think it’s a kind of blood cancer that only affects children. However, leukemia affects adults about 10 times as much as kids. And one type of leukemia, called myelofibrosis (MF), is primarily found in adults older than 50 years old.

Leukemia is the umbrella term used for cancers of the blood. MF is a rare type of leukemia that impacts how your body produces blood cells. In healthy people, stem cells in the bone marrow develop into blood cells. But in people with MF, scar tissue forms in the bone marrow, so it cannot make enough normal blood cells. The liver and spleen try to make some of the blood cells instead, which causes them to swell.

MF affects every patient differently: some people live for many years without developing symptoms, but others experience symptoms sooner and require treatment earlier on. Data shows that patients with MF live an average of five years after they’re diagnosed—but some people may live for decades. Such grim statistics predate the arrival of revolutionary MF therapies. Researchers are making a lot of progress in finding the cause and more effective treatments for this rare disorder.


Myelofibrosis is actually classified specifically as a myeloproliferative neoplasm (MPN), a term for a group of three progressive blood cancers in which the bone marrow is damaged so blood cell production is impaired. The other MPNs are called essential thrombocythemia (ET), characterized by a high level of platelets in the blood, and polycythemia vera (PV), which involves a high level of red blood cells in the blood. Sometimes, ET and PV can progress into MF—when this occurs, it’s called secondary myelofibrosis.

When MF develops without the presence of another disease, it’s called primary myelofibrosis. Experts don’t know the exact cause, but they believe primary MF may occur when the bone marrow produces abnormal stem cells. These abnormal stem cells grow quickly and take over the bone marrow, which creates scar tissue and inflammation; because of this, the bone marrow cannot create enough normal blood cells.

Researchers don’t know what triggers MF, but we do know that it’s most likely not inherited from family members. Recently, experts discovered that MF might be caused by mutations in specific genes. These breakthroughs have allowed scientists to develop more targeted treatments, so the outlook for people with MF is better than ever.

It’s also possible that MF can develop after someone is exposed to petrochemicals and ionizing radiation, but experts aren’t sure if this is definitely the case.


MF symptoms can vary, and usually patients look fine on the outside. But they may be experiencing difficult symptoms, including:

  • Fatigue, weakness, or shortness of breath after light activity—a result of not having enough blood circulating

  • A feeling of fullness or pain in the abdomen—a result of the spleen swelling up

  • Fever

  • Night sweats

  • Weight loss or malnutrition

  • Itching

  • Easy bleeding or bruising

  • Pain in the bones or joints, which sometimes develops into gout

  • Bloating in the abdomen related to excess fluid retention

  • Problems concentrating


Every case of MF is different, so physicians must use a variety of tests and exams to make a diagnosis. Your doctor will look at your medical history, do a physical exam, and then order some tests. During the physical exam, your doctor will be looking to see if you have an enlarged spleen, if you’re pale and have anemia (a condition in which you don’t have enough red blood cells circulating), if you’ve lost muscle mass, and if you’ve experienced weight loss or muscle atrophy.

Your doctor may also order some lab tests, including:

  • Blood tests: a complete blood cell count (CBC) can show if your blood cell levels are abnormal.

  • Bone marrow aspiration or biopsy: by removing a sample of your bone marrow, a doctor can examine it under a microscope to see if there are signs of MF.

  • Test for genetic mutations: since some people with MF have specific gene mutations, this test can help lead a physician to diagnosis.

  • Imaging tests: an image of the spleen, like an ultrasound, may show if the spleen is enlarged.


If you aren’t experiencing symptoms of MF, then you may not need to start treatment right away. Your doctor will monitor your condition regularly, and you should keep an eye out for signs and symptoms—but some people remain free of symptoms for years.

If you are experiencing symptoms, there are several options available to treat, and in some cases cure, MF, including:

Allogeneic Stem Cell Transplantation (ASCT)

This procedure is the only treatment option that actually cures MF. However, not every patient is eligible, given the complexity and risk of the transplantation process. In ASCT, stem cells are transferred from a healthy donor to the MF patient, replacing the defective stem cells with healthy ones. Before the infusion, patients receive chemotherapy or radiation (or both) to eliminate the bone marrow – allowing the donor stem cells to repopulate with a ‘clean slate’. This procedure is not recommended for older patients or those who have other chronic conditions.

Blood Transfusions

Patients with severe anemia resulting from MF may benefit from blood transfusions to provide them with the blood cells they need.

Hydroxyurea (Droxia, Hydrea)

Hydroxyurea is a medication that prevents the bone marrow from developing blood cells. Taking this medication can reduce the level of white blood cells and platelets in your blood, and reduce the size of your liver or spleen if they are enlarged.

Spleen Removal or Radiation

Some patients experience severe pain, anemia, a low platelet count, or hypertension as a result of an enlarged spleen. If other options don’t work to reduce the size of the spleen, surgery to remove it may be recommended. Your doctor may also try to radiation on the spleen. Both procedures are risky, so it’s important to weight the benefits and complications before undergoing either one.

Ruxolitinib (Jakafi)

Ruxolitinib is the first medication approved by the U.S. Food and Drug Administration (FDA) to treat MF. It works by blocking the overproduction of blood cells, and also can reduce the size of the spleen. Additionally, it may relieve some of the more minor symptoms, like night sweats, itchiness, weight loss, and fever. We’re not sure yet if ruxolitinib helps patients with MF live longer, but clinical trials are promising.


MF can lead to some serious complications, especially if it isn’t treated. You may develop blood clots that can cause a heart attack or stroke, and you may bleed more easily. Patients also are at risk of liver failure and developing infections. And about 20% of people with MF eventually develop an aggressive form of leukemia called acute myeloid leukemia (AML).

Researchers are working hard to determine the cause and best treatments for MF and there are several clinical trials studying novel treatments right now. For people with MF, there’s hope for a better outcome—but until we know more, the most important thing for patients to do is monitor their symptoms carefully and alert their doctors of any changes.


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Medical Reviewers: William C. Lloyd III, MD, FACS Last Review Date: Jun 24, 2016

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