Myelofibrosis

About Myelofibrosis


What is myelofibrosis?

Myelofibrosis (my-ah-lo-fye-BRO-sis), or MF, is a rare chronic blood cancer that affects the bone marrow and the production of blood cells. The bone marrow is the material inside the bone where blood cells are made. People with MF typically have:

  • Scarring in the bone marrow called fibrosis (fye-BRO-sis)
  • Too few or too many cells that make blood
  • Symptoms such as itching, night sweats, bone and muscle pain, abdominal discomfort, early feeling of fullness, and pain under the left ribs

Bone marrow is where blood cells are made. As scar tissue builds up, the bone marrow can’t make enough blood cells. The spleen, which is an organ near the stomach under the left ribs, partially takes over making blood cells. This may make the spleen get bigger, a condition called splenomegaly (splee-nuh-MEG-uh-lee).

Breaking down myelofibrosis:

myelo = bone marrow | fibrosis = scarring


Breaking down splenomegaly:

spleno = of the spleen | megaly = bigger than normal

Breaking down myelofibrosis:

myelo = bone marrow
fibrosis = scarring


Breaking down splenomegaly:

spleno = of the spleen
megaly = bigger than normal


Who gets MF?

65+ graphic

People are usually around 65 years old when they learn they have MF

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About 16,000 to 18,500 people in the United States have MF


What are the stages of MF?

It’s important to understand how MF can affect your body over time. In its very early stages, the disease may be silent. You might not experience symptoms even though the disease may be progressing. As the disease gets worse, its signs and symptoms start to increase.

Image of a healthcare professional talking with a patient

There are many things that can affect the course—or progression—of your MF. Researchers evaluate patients based upon these risk factors.


What causes MF?

MF is a complex condition that may have many contributing factors. We do know that certain proteins called Janus-associated kinases, or JAKs, are important. JAKs tell blood cells in the bone marrow to divide and grow.

When JAKs are working normally, they help the body make the right number of blood cells. But when JAKs aren’t working normally, they cause the body to make the wrong number of blood cells. They can also cause bone marrow scarring, an enlarged spleen, and symptoms.


MF can develop from other myeloproliferative neoplasms


MF is a chronic bone marrow condition that is part of a group of diseases called myeloproliferative neoplasms (MY-ah-lo-pro-LIF-er-uh-tiv NEE-o-plaz-uhms), or MPNs. If MF is a person’s first MPN, then it is called primary myelofibrosis.


Mutations, or changes, in genes are thought to be ultimately responsible for MF. The mutations may be in the genes that make JAKs, or the mutations may be in genes that affect how JAKs function. In either case, the mutations cause what is known as overactive JAK signaling.

Graphic of Normal Signaling of JAK proteins that affect the production of blood cells in the bone marrow.

Normal Signaling

Graphic of Overactive Signaling of JAK proteins causing the body to make the wrong number of blood cells.

Overactive Signaling

MF is a complex condition that may have many contributing factors. We do know that certain proteins called Janus-associated kinases, or JAKs, are important. JAKs tell blood cells in the bone marrow to divide and grow.

When JAKs are working normally, they help the body make the right number of blood cells. But when JAKs aren’t working normally, they cause the body to make the wrong number of blood cells. They can also cause bone marrow scarring, an enlarged spleen, and symptoms.

Mutations, or changes, in genes are thought to be ultimately responsible for MF. The mutations may be in the genes that make JAKs, or the mutations may be in genes that affect how JAKs function. In either case, the mutations cause what is known as overactive JAK signaling.

Graphic of Normal Signaling of JAK proteins that affect the production of blood cells in the bone marrow.

Normal Signaling

Graphic of Overactive Signaling of JAK proteins causing the body to make the wrong number of blood cells.

Overactive Signaling


MF can develop from other myeloproliferative neoplasms


MF is a chronic bone marrow condition that is part of a group of diseases called myeloproliferative neoplasms (MY-ah-lo-pro-LIF-er-uh-tiv NEE-o-plaz-uhms), or MPNs. If MF is a person’s first MPN, then it is called primary myelofibrosis.



In other cases, another MPN, like polycythemia vera (PV) or essential thrombocythemia (ET), can turn into MF. These conditions are called post–PV MF and post–ET MF. About 10-15% of patients with MF have these conditions.


What are the symptoms of MF?

Symptoms of MF can range from mild to severe. They may be caused by an enlarged spleen or by production of too many cytokines, proteins that cause inflammation.


As discussed previously, if your bone marrow is not making enough blood cells (or making them too quickly so that they don’t have time to fully form), your spleen can take over and begin to make blood cells. This may make your spleen get bigger.

Symptoms of an enlarged spleen include:

  • Abdominal discomfort
  • Pain under the left ribs
  • Early feeling of fullness
Graphic of 85% in circle – representing approximately 85% of people with MF have an enlarged spleen at diagnosis.

Approximately 85% or more of people with MF have an enlarged spleen at diagnosis.

Symptoms caused by overproduction of cytokines in the body include:

  • Itching
  • Night sweats
  • Bone pain
Graphic of 50% to 60% in circle – representing approximately 50% to 60% of people with MF report having itching, night sweats, and bone pain.

Approximately 50% to 60% of people with MF report having itching, night sweats, and bone pain.


What aspects of my MF should I be tracking?

An important goal of MF treatment is to reduce your symptoms. That’s why keeping track of your condition over time can be so important. People living with MF may get used to their symptoms, so it’s important to keep track of your health on a regular basis so that you can more easily identify when something has changed.

In addition to monitoring symptoms, you may also want to keep track of key blood cell counts and medical procedures, such as blood transfusions. If you recognize any changes in your symptoms, blood count levels, or the frequency of blood transfusions, be sure to discuss them with your Healthcare Professional.

One way to keep track of your MF is to use a tracking tool, symptom diary, or online tracker. You can also use the MPN Symptom Assessment Form (MPN SAF), a tool that helps measure the 10 most clinically relevant MPN symptoms. No matter what tracking tool you decide to use, be sure to report any changes in your health to your Healthcare Professional—even if you’re not sure that it’s related to your MF.

Remember, regular tracking over time may help you discover important insights that can help you and your Healthcare Professional better understand the state of your MF—and ensure that your current treatment approach is the right one for you.

Graphic of checklist on notepad with pencil

Download the MPN Symptom Assessment Form


How is MF treated?

Your Healthcare Professional will work with you to make a plan that is right for you. One option is Jakafi® (ruxolitinib). It is the first and only prescription medicine approved by the FDA to treat intermediate or high-risk MF.

Image of Sue – Watch her story and learn how her MF symptoms affected her before she started taking Jakafi.

Learn how the symptoms of MF affected Sue before she started taking Jakafi.

Discover how Sue’s MF symptoms prompted her to talk to her Healthcare Professional about moving her treatment journey forward with Jakafi.

Watch Sue’s Story
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Important Safety Information

Indications and Usage

Jakafi is a prescription medicine used to treat people with polycythemia vera who have already taken a medicine called hydroxyurea and it did not work well enough or they could not tolerate it.

Jakafi is also used to treat certain types of myelofibrosis.

Important Safety Information

Jakafi can cause serious side effects, including:

Low blood counts: Jakafi® (ruxolitinib) may cause your platelet, red blood cell, or white blood cell counts to be lowered. If you develop bleeding, stop taking Jakafi and call your healthcare provider. Your healthcare provider will perform blood tests to check your blood counts before you start Jakafi and regularly during your treatment. Your healthcare provider may change your dose of Jakafi or stop your treatment based on the results of your blood tests. Tell your healthcare provider right away if you develop or have worsening symptoms such as unusual bleeding, bruising, tiredness, shortness of breath, or a fever.

Infection: You may be at risk for developing a serious infection during treatment with Jakafi. Tell your healthcare provider if you develop any of the following symptoms of infection: chills, nausea, vomiting, aches, weakness, fever, painful skin rash or blisters.

Skin cancers: Some people who take Jakafi have developed certain types of non-melanoma skin cancers. Tell your healthcare provider if you develop any new or changing skin lesions.

Increases in cholesterol: You may have changes in your blood cholesterol levels. Your healthcare provider will do blood tests to check your cholesterol levels during your treatment with Jakafi.

The most common side effects of Jakafi include: low platelet count, low red blood cell counts, bruising, dizziness, headache.

These are not all the possible side effects of Jakafi. Ask your pharmacist or healthcare provider for more information. Tell your healthcare provider about any side effect that bothers you or that does not go away.

Before taking Jakafi, tell your healthcare provider about: all the medications, vitamins, and herbal supplements you are taking and all your medical conditions, including if you have an infection, have or had tuberculosis (TB) or have been in close contact with someone who has TB, have or had hepatitis B, have or had liver or kidney problems, are on dialysis, had skin cancer, or have any other medical condition. Take Jakafi exactly as your healthcare provider tells you. Do not change your dose or stop taking Jakafi without first talking to your healthcare provider. Do not drink grapefruit juice while on Jakafi.

Women should not take Jakafi while pregnant or planning to become pregnant, or if breast-feeding.

Please see the Full Prescribing Information, which includes a more complete discussion of the risks associated with Jakafi.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch, or call 1-800-FDA-1088.

You may also report side effects to Incyte Medical Information at 1-855-463-3463.