Myelofibrosis (MF) is a bone marrow cancer affecting blood cell production. It causes abnormal development and function of bone marrow cells, leading to scar tissues

Myelofibrosis (MF) is part of a group of conditions called myeloproliferative neoplasms (MPNs).

Other MPNs can also progress to MF. While some people can go years without having symptoms, others have symptoms that get worse due to scarring in their bone marrow.

The bone marrow consists of tissues responsible for producing blood cells, including red blood cells, white blood cells, and platelets. It is also made up of a network of fibers that support the blood-forming tissues.

There are two types of MF:


Primary MF develops on its own, causing many blood stem cells to turn into immature blood cells called blasts.

The web of fibers in the bone marrow also becomes abnormally thick, resembling scar tissue, which makes it harder for your body to make new blood cells.


Secondary MF results from another condition — usually one that affects your bone marrow. This includes polycythemia vera, chronic myeloid leukemia (CML), and essential thrombocythemia.

The end result is the same, and in addition to the symptoms of MF, you would also experience the symptoms of the underlying condition.

MF tends to come on slowly, and many people don’t notice symptoms at first. However, as it progresses and starts to interfere with blood cell production, its symptoms may include:

  • fatigue
  • shortness of breath
  • bruising or bleeding easily
  • feeling pain or fullness on your left side, below your ribs
  • night sweats
  • fever
  • bone pain
  • loss of appetite and weight loss
  • nosebleeds or bleeding gums

MF is associated with a genetic mutation in blood stem cells. However, researchers aren’t sure what causes this mutation.

When the mutated cells replicate and divide, they pass the mutation on to new blood cells. Eventually, the mutated cells overtake the bone marrow’s ability to produce healthy blood cells.

This usually results in too few red blood cells and too many white blood cells. It also causes scarring and hardening of your bone marrow, which is usually soft and spongy.

Generally speaking, MF is rare, occurring in only about 4-6 out of every 100,000 people in the United States.

Some sources suggest that primary MF is as rare as 0.8-2.1 per 100,000 people yearly. For secondary MF, the prevalence depends on the exact condition causing it.

However, several things can increase your risk of developing it, including:

  • Age: While people of any age can have MF, it’s usually diagnosed in those over the age of 50.
  • Another blood disorder.: Some people develop secondary MF as a complication of another condition.
  • Exposure to chemicals: MF has been associated with exposure to certain industrial chemicals, including toluene and benzene.
  • Exposure to radiation: People who’ve been exposed to radioactive material may have an increased chance of developing MF.

MF usually shows up on a routine complete blood count (CBC). People with MF tend to have very low levels of red blood cells and unusually high or low levels of white blood cells and platelets.

Based on the results of your CBC test, your doctor might also do a bone marrow biopsy. This involves taking a small sample of your bone marrow and looking at it more closely for signs of MF, such as scarring.

You may also need an X-ray or MRI scan to rule out any other potential causes of your symptoms or CBC results.

MF treatment usually depends on the types of symptoms you have. Many common MF symptoms are associated with an underlying condition caused by MF, such as anemia or an enlarged spleen.

Treating anemia

If MF is causing severe anemia, you may need:

  • Blood transfusions: Regular blood transfusions can increase your red blood cell count and reduce anemia symptoms, such as fatigue and weakness.
  • Hormone therapy: A synthetic version of the male hormone androgen may promote red blood cell production in some people.
  • Corticosteroids: These may be used with androgens to encourage red blood cell production or decrease their destruction.
  • Prescription medications: Immunomodulatory medications, such as thalidomide (Thalomid) and lenalidomide (Revlimid), may improve blood cell counts. They may also help with symptoms of an enlarged spleen.

Treating an enlarged spleen

If you have an enlarged spleen related to MF that’s causing problems, your doctor might recommend:

  • Radiation therapy: Radiation therapy uses targeted beams to kill cells and reduce the size of the spleen.
  • Chemotherapy: Some chemotherapy drugs may reduce the size of your enlarged spleen.
  • Surgery: A splenectomy is a surgical procedure that removes your spleen. Your doctor might recommend this if you aren’t responding well to other treatments.

Treating mutated genes

A drug called ruxolitinib (Jakafi) was approved by the Food and Drug Administration in 2011 to treat the symptoms associated with MF. Ruxolitinib targets a specific genetic mutation that may be the cause of MF.

In clinical trials, it was shown to reduce the size of enlarged spleens, reduce the symptoms of MF, and improve prognosis.

Additional drugs, Inrebic (fedratinib), Vonjo (pacritinib), and Ojjaara (momelotinib), were approved to treat certain types of MF in 2019, 2022, and 2023, respectively. Like Jakafi, these drugs all fall into the category of Janus Kinase (JAK) inhibitors.

Experimental treatments

Researchers are working on developing new treatments for MF. While many of these require further study to make sure they’re safe, doctors have started using two new treatments in certain cases:

  • Stem cell transplant: Stem cell transplants have the potential to cure MF and restore bone marrow function. However, the procedure can cause life threatening complications, so it’s usually only done when nothing else works.
  • Interferon-alpha: Interferon-alfa has delayed the formation of scar tissue in the bone marrow of people who receive treatment early on, but more research is needed to determine its long-term safety.

It’s difficult to predict the outlook for MF, especially in cases of secondary MF, as it depends on the root cause. In addition, there’s no staging system for MF.

People who are low risk tend to have a median survival of 15 years or longer. Certain factors can lower this time frame, including:

  • being older than 65
  • having too few red blood cells, too many white blood cells, or certain immature white blood cells
  • needing many blood transfusions
  • having certain chromosomal abnormalities
  • having generalized symptoms such as fever, weight loss, or fatigue

Roughly 10-20% of MF cases progress to AML, a difficult-to-treat form of cancer with a low survival rate.

Over time, MF can lead to several complications. Other than AML, they include:

Increased blood pressure in your liver.

Increased blood flow from an enlarged spleen can raise the pressure in the portal vein in your liver, causing a condition called portal hypertension.

This can put too much pressure on smaller veins in your stomach and esophagus, which could lead to excessive bleeding or a ruptured vein.


Blood cells can form in clumps outside the bone marrow, causing tumors to grow in other areas of your body.

Depending on where these tumors are located, they can cause a variety of different problems, including seizures, bleeding in the gastric tract, or compression of the spinal cord.

Is myelofibrosis curable?

There isn’t one single treatment that works the same for every person or every type of MF. The only true cure involves a stem cell transplant, but this can also cause complications and needs more research on its safety.

How painful is myelofibrosis?

With MF, you may feel some discomfort or pain below your ribs on the left side because of the enlarged spleen. It may also cause bone pain, as well as joint pain in some cases. The degree of pain can vary between people.

Do you lose weight with myelofibrosis?

Weight loss can be one of the symptoms of MF. This is usually related to a lower appetite and overall feeling of fullness caused by an enlarged spleen.

While MF often doesn’t cause symptoms in its early stages, it can eventually lead to serious complications, including more aggressive types of cancer.

Work with your doctor to determine the best course of treatment for you and how you can manage your symptoms.

Living with MF can be stressful, so you may find it helpful to seek out support from an organization such as the Leukemia and Lymphoma Society or the Myeloproliferative Neoplasm Research Foundation. Both organizations can help you find local support groups, online communities, and even financial resources for treatment.