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Myelofibrosis (MF)

  • Is a rare disorder in which abnormal blood cells and fibers build up in the bone marrow.
  • Is one of a related group of blood cancers known as “myeloproliferative neoplasms (MPNs)” in which bone marrow cells that produce blood cells develop and function abnormally. 

What You Should Know

  • Hematologists oncologists are specialists who treat people who have myelofibrosis (MF) or other types of blood cancer.
  • MF usually develops slowly and some people may live symptom-free for years. Others, however, may get progressively worse, requiring treatment. In both cases, patients do need to be monitored regularly.
  • The treatment goal for most patients with MF is to relieve symptoms, reduce an enlarged spleen, improve blood cell counts (i.e., anemia), and reduce the risk of complications. 

What You Should Do

  • Talk with your doctor about your diagnostic tests and what the results mean.
  • Talk with your doctor about all your treatment options, side effects, and the results you can expect from treatment.
  • Ask your doctor whether a clinical trial is a good treatment option for you.

How Does MF Develop?

The DNA (genetic material) of a single hematopoietic (blood-forming) stem cell is damaged. This is called an “acquired mutation.”

  • Stem cells form blood cells (white cells, red cells and platelets). 

As the mutated stem cell copies itself and divides, it multiplies uncontrollably, creating many abnormal immature blood cells called “blasts.” These blasts do not mature into healthy blood cells nor do they function as healthy blood cells. Over time, the creation of abnormal blasts surpasses the bone marrow’s ability to produce normal healthy blood cells.

  • Red blood cells carry oxygen to the tissues.
  • White blood cells fight infection.
  • Platelets help blood to clot.

Over time, the fibrous tissue impairs the bone marrow’s ability to produce normal blood cells. As a result, the bone marrow makes fewer and fewer healthy blood cells.

  • When the bone marrow is unable to make enough healthy red blood cells, anemia often results. Symptoms of anemia include fatigue, weakness and shortness of breath. 
  • When the bone marrow cannot make enough healthy white blood cells, a patient may also be more susceptible to getting an infection.
  • A reduction in platelets can cause easy bleeding and bruising. 
  • The abnormal growth of blood-forming cells can also take place outside of the bone marrow, called “extramedullary hematopoiesis,” in such organs as the liver, spleen, lungs, lymph nodes and spinal cord, causing swelling.

Researchers theorize that mutated hematopoietic stem cells may change the environment of the bone marrow by releasing chemicals that can cause the spongy bone marrow to become scarred (fibrous). 

  • One blood cell thought to contribute to the fibrous tissue is the giant cell in the bone marrow called the “megakaryocyte.”
  • Huge megakaryocytes break up into fragments in the bone marrow and produce hundreds to thousands of platelets.
  • With MF, the bone marrow creates too many abnormal megakaryocytes. These megakaryocytes release substances called “cytokines,” which some researchers believe may cause inflammation and stimulate the buildup of more fibrous tissue in the bone marrow. 

Source: Myeloproliferative Neoplasms. Reviewed by John Mascarenhas, MD.