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Idiopathic myelofibrosis

Idiopathic myelofibrosis (IM) is also called primary myelofibrosis or chronic idiopathic myelofibrosis. It is a myeloproliferative neoplasm that starts when blood cells don’t develop normally. Sometimes polycythemia vera (PV) or essential thrombocytosis (ET) develops into idiopathic myelofibrosis.

Idiopathic myelofibrosis is a chronic disorder, which means that it develops slowly over time. Eventually it causes fibrous, or scar, tissue to form in the bone marrow. The scarring means the bone marrow can’t work normally. It makes fewer red blood cells and usually too many white blood cells. Platelets may be increased or decreased. Fibrous tumours may also develop outside of the bone marrow.

Doctors don’t know what causes idiopathic myelofibrosis, but about half of the people with this disease have a change, or mutation, in the JAK2 (Janus kinase 2) gene. What causes this gene mutation is not known.

Idiopathic myelofibrosis can develop at any age but is more common in older people. People with idiopathic myelofibrosis have an increased risk of developing acute myelogenous leukemia (AML).


Idiopathic myelofibrosis may not cause any signs or symptoms in its early stages. Symptoms develop as more scar tissue forms in the bone marrow and it can’t work normally.

See your doctor if you have these symptoms:

  • fatigue
  • weakness
  • paleness
  • shortness of breath
  • bruising
  • weight loss
  • fever
  • frequent infections
  • night sweats
  • feeling full after eating a small amount
  • discomfort or a feeling of fullness in the abdomen (if the liver and spleen are enlarged)
  • bone pain

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Diagnosing idiopathic myelofibrosis usually begins with a trip to your family doctor or when a routine blood test suggests a problem with the blood. Your doctor will ask you about any symptoms you have and do a physical exam to check if your spleen or liver is enlarged. Based on this information, your doctor will order tests to check for idiopathic myelofibrosis or other health problems.

Some of the same tests used to rule out or diagnose leukemia are used to diagnose idiopathic myelofibrosis. These tests include:

  • complete blood count (CBC) to measure the number and quality of white blood cells, red blood cells and platelets
  • blood chemistry tests to show how well certain organs are working
  • reverse transcriptase polymerase chain reaction (RT-PCR) to see if cells in a sample of blood and bone marrow have the JAK2 mutation
  • bone marrow aspiration and biopsy to confirm whether or not you have idiopathic myelofibrosis

Find out more about these tests and procedures.

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Your healthcare team will create a treatment plan just for you. The goal of treatments for idiopathic myelofibrosis is to relieve symptoms and lower the risk of complications. If you don’t have any symptoms, you probably don’t need treatments. Many people who don’t have any symptoms don’t need any treatments for years.

People with idiopathic myelofibrosis may be treated with different drugs. For more information on certain drugs, go to sources of drug information.

Drug therapy

Drugs may be used alone to improve blood cell counts or lessen symptoms. These drugs include:

  • ruxolitinib (Jakavi)
  • hydroxyurea (Hydrea)
  • interferon alfa (Intron A, Wellferon)
  • danazol (Danocrine)
  • prednisone
  • anagrelide (Agrylin)
  • lenalidomide (Revlimid)

Supportive therapy

You may be offered iron and folate supplements if you have anemia. If the anemia is severe, you may need to have blood transfusions.

Bisphosphonates are drugs that stop the body from breaking down bone. They also help strengthen bones. You may be given the bisphosphonate zoledronic acid (Zometa) if you have idiopathic myelofibrosis.

Radiation therapy

Radiation therapy uses high-energy rays or particles to destroy cancer cells. During external beam radiation, a machine directs radiation through the skin to the tumour and some of the tissue around it.

Some people with idiopathic myelofibrosis will have external beam radiation therapy. It can be used to treat an enlarged spleen, bone pain or tumours that develop outside of the bone marrow.


Surgery to remove the spleen (called splenectomy) may be done if an enlarged spleen is causing pain. It can also be done to help return blood cell counts to normal.

Stem cell transplant

A stem cell transplant may be a treatment option for some younger people who have advanced idiopathic myelofibrosis.

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Follow-up after treatment is an important part of cancer care. Follow-up for idiopathic myelofibrosis is often shared among the cancer specialists (oncologists) or blood specialists (hematologists) and your family doctor. Your healthcare team will work with you to decide on follow-up care to meet your needs.

Don’t wait until your next scheduled appointment to report any new symptoms and symptoms that don’t go away.

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