- Is a rare bone marrow cancer. It is one of a related group of blood cancers known as “myeloproliferative neoplasms (MPNs)” in which bone marrow cells that produce the blood cells develop and function abnormally. The resulting fibrous scar tissue formation leads to severe anemia, weakness, fatigue and an enlarged spleen and liver.
- Is a type of chronic leukemia and can occur on its own (primary myelofibrosis) or as a result of another bone marrow disorder. Other MPNs that can progress to myelofibrosis include polycythemia vera and essential thrombocythemia.
What You Should Know
- Hematologists and 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.
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 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 developing stem cell in the bone marrow is damaged. This is called an “acquired mutation.”
- Stem cells form blood cells (white cells, red cells and platelets).
As the mutated blood cell replicates and divides, it passes along the mutation to new cells. Eventually, this abnormal cell production overtakes the bone marrow’s ability to produce enough normal blood cells, including
- Red blood cells, which carry oxygen to the tissues
- White blood cells, which fight infection
- Platelets, which help blood to clot.
When the bone marrow is unable to make enough healthy blood cells, the result can be severe anemia, weakness, bone pain, fatigue and increased risk of infection.
- 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.
An important constant feature of MF is the overproduction of platelet-forming cells, called "megakaryocytes," in the marrow. This leads to the release of chemicals called "cytokines.” The cytokines stimulate the development of scar tissue in the marrow, called fibrosis.
- The platelets' normal function is to stick to the site of a blood vessel injury and form a plug (clot) to seal off the injured blood vessel to stop bleeding. The body makes new platelets to replace used platelets. With MF, the megakaryocytes can become so abnormal that platelet production decreases in some patients.
- Myelofibrosis gets its name from the disease's characteristics. The prefix "myelo-" in the word "myelofibrosis" means a relationship to the marrow. The presence of scar tissue gives the disease the "fibrosis" part of its name. MF is also known by several other names, including agnogenic myeloid metaplasia and idiopathic myelofibrosis.
For most people who have myelofibrosis (MF), there are no obvious reasons (risk factors) why they developed the disease. The disease starts as one of two other myeloproliferative diseases, either polycythemia vera or primary thrombocythemia, in about 10 percent to 15 percent of people with MF.
Doctors don't fully understand the cause of MF. About half of all patients with MF have a mutation (change in their DNA) called "V617F JAK2" (Janus kinase 2) found in the JAK2 gene. This mutated gene may play a role in MF's onset. However, researchers are still studying its precise role as the cause of the disease.
Between 5 and 10 percent of MF patients will have a myeloproliferative leukemia (MPL) gene mutation. Like JAK2, this gene is also the subject of research to determine what role it plays in MF development.
Source: Myelofibrosis Facts. Reviewed by Ayalew Tefferi, MD.