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Myelofibrosis is a disorder of the bone marrow in which the marrow is replaced by fibrous scar tissue.

Alternative Names

Idiopathic myelofibrosis; Myeloid metaplasia; Agnogenic myeloid metaplasia; Primary myelofibrosis; Secondary myelofibrosis; Bone marrow - myelofibrosis


Bone marrow is the soft, fatty tissue inside your bones. Stem cells are immature cells in the bone marrow that develop into all of your blood cells. Your blood is made of:

  • Red blood cells (which carry oxygen to your tissues)
  • White blood cells (which fight infection)
  • Platelets (which help your blood clot)

When the bone marrow is scarred, it cannot make enough blood cells. Anemia, bleeding problems, and a higher risk for infections may occur.

As a result, the liver and spleen try to make some of these blood cells. This causes these organs to swell.

The cause of myelofibrosis is unknown. There are no known risk factors. When it occurs, it often develops slowly in people over age 50.

Blood and bone marrow cancers such as myelodysplastic syndrome, leukemia, and lymphoma may also cause bone marrow scarring. This is called secondary myelofibrosis.


Symptoms may include any of the following:

Exams and Tests

The health care provider will perform a physical exam and ask about the symptoms.

Tests that may be done include:


Bone marrow or stem cell transplant may improve symptoms, and may cure the disease. This treatment is usually considered for younger people.

Other treatment may involve:

  • Blood transfusions and medicines to correct anemia
  • Radiation and chemotherapy
  • Medicines to target a genetic mutation linked to this disease, if present
  • Removal of the spleen (splenectomy) if swelling causes symptoms, or to help with anemia

Outlook (Prognosis)

As the disease worsens, the bone marrow slowly stops working. Low platelet count leads to easy bleeding. Spleen swelling may get worse along with anemia.

Survival of people with primary myelofibrosis is about 5 years. But some people survive for decades.

Possible Complications

Complications may include:

When to Contact a Medical Professional

Make an appointment with your provider if you have symptoms of this disorder. Seek medical care right away for uncontrolled bleeding, shortness of breath, or jaundice (yellow skin and whites of the eyes) that gets worse.


Mascarenhas J, Najfeld V, Kremyanskaya M, Hoffman R. Primary myelofibrosis. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, Anastasi J, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:chap 69.

Tefferi A. Polycythemia vera, essential thrombocythemia, and primary myelofibrosis. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 166.

Version Info

  • Last reviewed on 5/20/2016
  • Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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