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What Is Prefibrotic Myelofibrosis?
Posted: Mar 19, 2024
What Is Prefibrotic Myelofibrosis? image

In 2016, the WHO (World Healthcare Organization) classified two stages of primary myelofibrosis (PMF): early/prefibrotic PMF (pre-PMF) and overt PMF. We generally focus on primary myelofibrosis. However, pre-PMF is a rare, distinct, and progressive blood cancer that can evolve into PMF and acute leukemia. 

A Closer Look At Pre-PMF

Pre-PMF is an earlier stage of the disease compared to overt primary myelofibrosis (PMF). Patients with pre-PMF might not experience all the symptoms typically associated with myelofibrosis. The key difference between the two is in the bone marrow, the spongy tissue inside the bones where blood cells are produced.

In pre-PMF, there is minimal or no noticeable bone marrow fibrosis (scarring) compared to overt PMF, where fibrosis is more prominent and significantly disrupts blood cell production.

  • Pre-PMF: fibrosis grade 0-1. This is a non-mild form of reticulin (a protein resembling collagen present in connective tissue).
  • PMF: fibrosis grade 2-3. These are dense-extensive bundles of reticulin fibers.

Patients with pre-PMF might not experience all the symptoms typically associated with myelofibrosis, but it can mimic the symptoms of other similar diseases like essential thrombocythemia (ET). For an accurate diagnosis, it will be important to rule out all other options; for that, a bone marrow biopsy will be required.

How is Pre-PMF Diagnosed?

A clinical and bone marrow examination will show the following:

  • Altered blood work with anemia and a high white blood cell count.
  • An enlarged spleen.
  • A large number of bone marrow cells that produce platelets.
  • A high amount of granulocytes, a type of white blood cell.
  • A decrease in the production of red blood cells.
  • The presence of mutations in the JAK2, CALR, or MPL genes.

What is the Risk of Pre-PMF Converting Into Overt PMF?

While pre-PMF may not cause immediate symptoms, it's important to be aware of and monitor the condition closely. Early diagnosis and management can help improve a patient's long-term health.

Pre-PMF is classified according to the likelihood of it progressing to overt PMF and survival. Several factors can increase the odds, including:

  • Older age
  • Higher frequency of symptoms like fever, night sweats, and unexplained weight loss.
  • An enlarged spleen.
  • A lower platelet count. 
  • Certain gene mutations.

Patients then can be classified into

  • Low-risk: Patients have the best prognosis and may not require any therapeutic intervention. Observation alone is usually recommended.
  • Intermediate-risk: Patients might need some treatments for their symptoms and have a higher risk of progressing. 
  • High-risk: Patients have the poorest prognosis and will require more intensive treatment options like stem cell transplantation for eligible patients and enrollment in clinical trials.

See Healthtree's Clinical Trial Finder HERE.

How Long Do Patients Live with Pre-PMF?

The survival of patients with pre-PMF is directly linked to potentially progressing to PMF, and even between patients in the same risk group, there is a lot of variability in disease progression. Other factors like overall health or other medical conditions can also affect survival. However, studies report a median overall survival for pre-PMF patients ranging from 8 years to over 20 years. 


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The author Lisa Foster

about the author
Lisa Foster

Lisa Foster is a mom of 3 daughters, a puzzle lover, writer and HealthTree advocate. She believes in the mission of the foundation and the team that builds it forward. She calls Houston, Texas home. 

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