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Myelofibrosis (MF)

  • Is a rare type of blood cancer characterized by the buildup of scar tissue, called “fibrosis,” in the bone marrow. As scar tissue increases, the bone marrow cannot make enough healthy blood cells
  • 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. 

When myelofibrosis develops on its own (and not as the result of another bone marrow disease) it is called “primary myelofibrosis.” In other cases, another type of MPN, such as polycythemia vera (PV) or essential thrombocythemia (ET), can transform into MF. In these cases, it is known as “secondary MF,” which may also be referred to as a “post-PV MF” or “post-ET MF.” Between 10 and 20 percent of all MF cases begin as either PV or ET.

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.

To download lists of suggested questions to ask your healthcare providers, click here.

How Does MF Develop?

The cause of primary MF is not fully understood. It is a complex disease that may have many contributing factors. Researchers believe that proteins known as Janus kinases (JAKs) are involved. These proteins send signals that affect the production of blood cells in the bone marrow. They also help control the number of red blood cells, white blood cells and platelets. When JAKs are working normally, they help the body make the right number of blood cells. But when too many signals are sent by these proteins, it causes too many blood cells to be made in the bone marrow

As the mutated overactive blood stem cell divides and makes copies of itself, it multiplies uncontrollably, creating many abnormal megakaryocytes in the bone marrow. (Megakaryocytes are the cells that produce platelets). These abnormal megakaryocytes may change the environment of the bone marrow by releasing cytokines. Some researchers believe this may cause inflammation and stimulate the buildup of fibrous tissue in the bone marrow. The web of fibers inside the bone marrow then becomes thick, like scar tissue. Over time, the fibrous tissue impairs the bone marrow’s ability to produce normal blood cells, leading to symptoms and complications. 


Source: Myeloproliferative Neoplasms. Reviewed by Jeanne Palmer, MD.