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Primary Myelofibrosis

Last updated Dec. 20, 2018

Approved by: Maulik P. Purohit MD, MPH

Primary Myelofibrosis is an acquired scarring (fibrosis) of the bone marrow (“myelo-“) that is not a consequence of another disease or condition (primary).

What are the other Names for this Condition? (Also known as/Synonyms)

  • Chronic Idiopathic Myelofibrosis
  • Idiopathic Myeloid Metaplasia
  • MMM (Myelofibrosis with Myeloid Metaplasia)

What is Primary Myelofibrosis? (Definition/Background Information)

  • Primary Myelofibrosis is an acquired scarring (fibrosis) of the bone marrow (“myelo-“) that is not a consequence of another disease or condition (primary)
  • Bone marrow is the spongy tissue found inside bones. Normally, it is the main site of blood cell production (hematopoiesis). The blood cells include:
    • Red blood cells (erythrocytes), which transport ‘gases’, such as oxygen
    • White blood cells (leukocytes), important to the immune system
    • Megakaryocytes, which fragment to form platelets. Platelets clot blood and recruit collagen-producing cells (fibroblasts) to the scene of an injury
  • Platelets and megakaryocytes normally recruit fibroblasts, only when they encounter blood vessel damage. The fibroblasts lay down scar tissue to promote closure of a wound
  • Myelofibrosis is the pathogenic result of inappropriate fibroblast activity in bone marrow. It is caused by the increased production of megakaryocytes and then platelets. Both of these contribute to excess fibroblast recruitment
  • During myelofibrosis, bone marrow is gradually replaced by fibrous scar tissue. The presence of scar tissue means that there is less bone marrow to perform hematopoiesis. Thus, fewer blood cells are formed, which impairs the body’s ability to transport oxygen, fight infection, and clot blood
  • The prognosis of Primary Myelofibrosis depends on the severity of the marrow condition and its response to treatment

Who gets Primary Myelofibrosis? (Age and Sex Distribution)

Individuals at risk for Primary Myelofibrosis include: 

  • Adult individuals between the ages of 50-80 years
  • Both men and women are at risk

This bone marrow disorder is a rare disease that affects 1 in 500,000 individuals, across the globe.

What are the Risk Factors for Primary Myelofibrosis? (Predisposing Factors)

Following are factors that increase one’s susceptibility to Primary Myelofibrosis:

  • Smoking
  • Exposure to radiation
  • Exposure to certain industrial chemicals
  • Chemotherapy
  • In rare cases, certain viruses

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Primary Myelofibrosis? (Etiology)

  • Primary Myelofibrosis is a result of detrimental genetic changes that occur after birth (somatic mutations). These occur in the regions of DNA that give instructions for proteins involved with the growth and division (proliferation) of blood cells, especially the platelet-producing megakaryocytes. This disorder is thus called a ‘myeloproliferative disorder’
  • The mutated proteins are hyperactive and result in overstimulation of megakaryocyte production. The increased megakaryocyte and platelet production results in excess fibroblast recruitment. The fibroblasts then lay down fibrous collagen tissue over the bone marrow and produce fibrosis
  • Bone marrow, experiencing fibrosis becomes distorted and is less able to produce blood cells. Also, the cells are sometimes released into circulation, before they have time to fully mature, or they are damaged, while being released. The presence of such cells is a telltale sign of a bone marrow disorder

What are the Signs and Symptoms of Primary Myelofibrosis?

Indicators for Primary Myelofibrosis include:

  • Abdominal pain and fullness, especially just below the left side of the rib cage
  • Shortness of breath, fatigue
  • Susceptibility to infection
  • Easy bruising
  • Persistent bleeding
  • Presence of kidney stones
  • Fever
  • Night sweats
  • Bone pain
  • Pale appearance (pallor)

How is Primary Myelofibrosis Diagnosed?

Following are the diagnostic techniques that aid in identification of Primary Myelofibrosis:

  • Physical examination and evaluation of medical history to detect:
    • Enlarged spleen (splenomegaly)
    • Enlarged liver (hepatomegaly)
  • Blood smear tests to detect:
    • Immature blood cells (leukoerythroblastosis)
    • Enlarged platelets (megathrombocytes)
    • Teardrop-shaped cells (dacryocytes)
    • Low counts of red blood cells (anemia)
  • Bone marrow biopsy to detect:
    • Elevated counts of marrow cells; indicative of early-stage Primary Myelofibrosis
    • Scarring (fibrosis); indicative of medium-stage Primary Myelofibrosis
    • Calcification; indicative of late-stage Primary Myelofibrosis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Primary Myelofibrosis?

Following are complications that may arise from Primary Myelofibrosis:

  • Severe infections
  • Formation of a blood clot inside blood vessels (thrombosis)
  • Excessive bleeding, especially during surgery
  • Transformation to acute myeloid leukemia (AML)
  • Obstruction of blood supply to the spleen, resulting in acute spleen infarction
  • Secondary gout
  • Formation of kidney stones

How is Primary Myelofibrosis Treated?

The treatment options for Primary Myelofibrosis include:

  • Bone marrow transplant
  • Chemotherapy, if the disease in its early-stage, and administration of the following drugs:
    • Thalidomide
    • Melphalanine
    • Interferon-alpha
    • Kinase inhibitors
  • Chronic blood infusions
  • Iron chelation therapy
  • Surgical removal of parts of the enlarged spleen (splenectomy)

How can Primary Myelofibrosis be Prevented?

Primary Myelofibrosis may be avoided by:

  • Limiting (exposure to) the following factors:
    • Radiation
    • Industrial chemicals
    • Chemotherapy
  • Quitting smoking

What is the Prognosis of Primary Myelofibrosis? (Outcomes/Resolutions)

  • Primary Myelofibrosis, if left untreated, has a poor prognosis and may cause death within 3-5 years
  • However, individuals may live up to 30 years, if the condition is mild, or is receptive to an appropriate treatment

Additional and Relevant Useful Information for Primary Myelofibrosis:

Myelodysplastic syndromes (MDS) are a group of conditions characterized by the disordered development of all non-lymphocyte blood cells (called myeloid cells). MDS is caused by various abnormalities of the bone marrow.

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 2, 2014
Last updated: Dec. 20, 2018