An Overview of Myelofibrosis

A disease of the bone marrow

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Myelofibrosis, also known as agnogenic myeloid metaplasia, is a rare and potentially serious disease of the bone marrow. It causes the marrow to develop fibrous tissue, which leads the marrow to produce abnormal blood cells. This can cause problems with cell counts and other serious complications, some of which can be fatal.

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This disorder affects both men and women. It can occur at any age but usually is diagnosed in people between 50 and 70 years old. Only about three people out of every 200,000 will develop this disease, which comes in several different forms.

Is It Cancer?

A lot of websites refer to myelofibrosis as "a rare blood cancer." That's a simple way to sum it up, but it's not technically correct.

Myelofibrosis is classified as a myeloproliferative neoplasm, which is a group of disorders that all include overproduction of at least one type of blood cell. These conditions have some similarities to cancer, but are not necessarily cancerous. The growths they cause can be benign (noncancerous), malignant (cancerous), or precancerous.

Myelofibrosis can increase your risk of some blood cancers, and it can also be caused by blood cancers.

What Bone Marrow Does

Bone marrow's main job is to create new blood cells. When fibrosis damages healthy bone marrow, abnormal cell counts and blood-cell abnormalities may result. In advanced cases, the marrow may completely fail, leading to severe complications, such as acute leukemia (a life-threatening blood cancer) or serious problems with bleeding and blood clotting.


As many as 25% of people with myelofibrosis have no symptoms.

Those who do have symptoms may experience:

  • An enlarged spleen, which causes discomfort in the upper-left abdomen or pain in the upper-left shoulder
  • Anemia, which can lead to fatigue and weakness
  • Shortness of breath
  • Fever
  • Weight loss
  • Night sweats
  • Unexplained bleeding
  • Bleeding and clotting problems due to the impact on blood platelets

How Is the Spleen Involved?

The spleen becomes involved because your body is trying to produce red blood cells wherever it can, which isn't supposed to happen.

Before babies are born, their bodies can produce new blood cells in the bone marrow, spleen, liver, and lymph nodes. Around the time of birth, though, blood-cell production becomes solely a function of bone marrow.

Dysfunction of the bone marrow causes your body to revert back to producing red blood cells in other locations, which can put a strain on those organs.


Some of the more serious complications of myelofibrosis may include:

  • Tumors made of developing blood cells forming outside the bone marrow
  • Slowed blood flow to the liver, leading to a condition called portal hypertension
  • Distended veins in the esophagus, known as esophageal varices, which may rupture and bleed


Myelofibrosis can be primary or secondary. Primary means that it wasn't caused by another illness, while secondary means that it was.

Primary Myelofibrosis

Experts aren't yet sure what causes primary, or idiopathic, myelofibrosis. They've linked several genes and types of marrow cells to the condition, including a genetic mutation called the JAK2 V617F missense mutation.

However, researchers don't know what causes the mutation, and not everyone with this mutation will develop the disease.

Secondary Myelofibrosis

Secondary myelofibrosis can be caused by:

While the disease is called simply myelofibrosis regardless of the cause, researchers believe there's still much to learn about the differences between each type.


Your healthcare provider may begin to suspect myelofibrosis due to your symptoms and/or a physical exam.

They can then order several tests to aid in the diagnosis, including:

  • Blood counts
  • Other blood work
  • Imaging tests such as X-rays and MRI
  • Bone marrow biopsy
  • Genetic tests

They may also test you for other conditions that can look like myelofibrosis, such as:


Right now, there's no drug that cures myelofibrosis. Treatments are intended to relieve symptoms and prevent complications, improve blood cell counts, and, if necessary, reduce an enlarged spleen.

Treatment is guided by:

  • Whether or not you're symptomatic
  • The risks involved with your specific case
  • Your age and overall health

If you don't have symptoms and are at low risk for complications, you may just need observation.

The drug Jakafi (ruxolitinib) is approved by the Food and Drug Administration (FDA) for treating intermediate and high-risk myelofibrosis, including primary myelofibrosis, post-polycythemia vera myelofibrosis, and post-essential thrombocythemia myelofibrosis. 

In February 2022, the FDA approved Vonjo (pacritinib) to treat intermediate or high-risk primary or secondary myelofibrosis in adults with platelet levels below 50,000/µL. Other drugs that can be used include Inrebic (fedratinib) and Hydrea (hydroxyurea).

For high-risk cases, healthcare providers sometimes consider transplanting stem cells from a donor, but this comes with some risks, and not everyone is eligible.

Enlarged Spleen

Treatments for an enlarged spleen include:

  • Medications, including Jakafi and Vonjo
  • Chemotherapy
  • Low-dose radiation therapy
  • Bone marrow (stem cell) transplantation
  • Splenectomy (surgical removal of the spleen)


If anemia is a problem for you, it may be treated with:

  • Iron supplements
  • Folate supplements
  • Blood transfusions
  • Medications, including bone-marrow stimulators, androgens, and immunomodulators


On average, individuals with myelofibrosis survive for five years after diagnosis. About 20% of individuals with the disorder survive 10 years or more.

The people with the best prognosis are those with hemoglobin levels above 10 g/dL, platelet counts above 100,000/uL, and those with less liver enlargement.

A Word From Verywell

The prognosis for someone with myelofibrosis may sound dire, but keep in mind that those numbers are historical. The outlook is continuously improving as new treatments are developed and researchers learn more about the disorder. Talk to your healthcare provider about what you can do to treat your illness, take care of yourself, and increase your odds of beating this disease.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Mary Kugler, RN
Mary Kugler, RN, is a pediatric nurse whose specialty is caring for children with long-term or severe medical problems.