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Myelofibrosis is a myeloproliferative neoplasm (MPN) where scar tissue (fibrosis) builds up in the bone marrow. As more scar tissue forms, the bone marrow can't make enough healthy blood cells. Myelofibrosis is also called primary myelofibrosis or chronic idiopathic myelofibrosis. Sometimes polycythemia vera and essential thrombocythemia develop into myelofibrosis, which is called secondary myelofibrosis.

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

Doctors don’t know what causes primary myelofibrosis, but about half of the people with this disease have a change (mutation) in the JAK2 (Janus kinase 2) gene. Changes in other genes are also seen in myelofibrosis.

Myelofibrosis may not cause any signs or symptoms in its early stages. Anemia and an enlarged spleen (splenomegaly) are common signs of myelofibrosis.

Diagnosing myelofibrosis usually begins when a routine blood test or the symptoms you have suggest a problem with the blood. Your doctor may order tests, such as a complete blood count (CBC) and a bone marrow aspiration and biopsy, to check for myelofibrosis or other health problems.


Your healthcare team will create a treatment plan just for you. The plan is based on your health and specific information about the disease. What you want is also important when planning treatment. When deciding which treatments to offer for myelofibrosis, your healthcare team will consider:

  • any symptoms you have
  • your risk group based on the number of risks you have, such as older age and abnormal blood cell counts

Treatments for myelofibrosis are used to relieve symptoms. Drug therapy is the main treatment for myelofibrosis. If you don’t have any symptoms, you probably don’t need treatments, but you will be closely monitored (called watch and wait).

Drug therapy

Drug therapy is used to improve blood cell counts and help control symptoms of myelofibrosis. You may be offered one or more of the following drugs.

JAK inhibitors are used to stop the activity of the Janus kinase proteins. Ruxolitinib (Jakavi) and fedratinib (Inrebic) are JAK inhibitors that may be used for myelofibrosis.

Chemotherapy may be used when there are too many platelets, too many white blood cells or an enlarged spleen. A chemotherapy drug that may be given is hydroxyurea (Hydrea).

Anagrelide (Agrylin) may be used to lower a high platelet count.

Androgen therapy, such as danazol (Cyclomen), is treatment with male hormones that may be used to increase the number of red blood cells.

Peginterferon alfa (Pegasys) is a cytokine used to boost the immune system to fight the disease.

Growth factors, such as epoetin alfa (Eprex), may be used to increase the number of red blood cells.

Bisphosphonates stop the body from breaking down bone, strengthen bone and help manage bone pain. You may be given zoledronic acid (Zometa) if you have myelofibrosis.

Find out more about sources of drug information and where to get details on specific drugs.

Blood transfusions

You may be offered blood transfusions to treat severe anemia.

Surgery to remove the spleen

Surgery to remove the spleen (called a splenectomy) is rarely done. It could be considered if an enlarged spleen is causing pain and drug therapy has not worked.

Stem cell transplant

An allogeneic stem cell transplant may be a treatment option for younger people who have advanced myelofibrosis.

Find out more about stem cell transplants.

Clinical trials

Talk to your doctor about clinical trials open to people with MPNs in Canada. Clinical trials look at new ways to prevent, find and treat diseases. Find out more about clinical trials.


Follow-up after treatment is an important part of cancer care. Follow-up for 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.

Expert review and references

  • Kareem Jamani, MD, LMCC, FRCPC

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