What Is Myelofibrosis?

Myelofibrosis is a chronic disease, which means that it will require management over time. By working with your healthcare team, you may be able to better navigate your symptoms. Listen as Dr. John Mascarenhas, a hematologist oncologist, explains what myelofibrosis is, how it presents and how it is diagnosed.

Learning about MF is the first step to helping you navigate all aspects of this disease. Talk to your healthcare provider to learn more.

View Transcript

Mapping Myelofibrosis Logo

Navigating a Rare Blood Cancer

Understanding Myelofibrosis with Dr. John Mascarenhas
What is Myelofibrosis?

Myelofibrosis is a blood cancer.

Dr. John Mascarenhas
Hematologist Oncologist

“So myelofibrosis is a blood cancer. It comes from the bone marrow. It results in fibrosis or scarring in the bone marrow, and often low blood counts that can really impact patients, so patients often do not feel well. They are going to have a lot of different symptoms, and it can really be debilitating. Unfortunately, it's a chronic disease, meaning it doesn't spontaneously remit. It is eventually progressive. It can progress in different ways for different patients. I'm not sure there's a typical presentation, actually. The presentations can be wide and varied. I really think it's very heterogeneous and variable the way patients present in their clinical course.”

What are the signs and symptoms of myelofibrosis?

“So sometimes you see patients present to a primary physician with complaints that might be protean, systemic symptoms like fevers, night sweats, weight loss. Then the workup ensues, and perhaps blood counts are abnormal. That then triggers a referral to a hematologist who then ultimately does a bone marrow biopsy and the diagnosis is made.”

“Sometimes patients end up in the emergency room, sometimes for clotting reasons, bleeding reasons, or acute issues, and then the diagnosis may be ultimately made. Then sometimes patients really are misdiagnosed or not correctly diagnosed and given a different diagnosis, perhaps like myelodysplastic syndromes or other diseases that can masquerade or be mimics of myelofibrosis, and I've seen that happen until it finally is confirmed.”

“So it really can be quite different. I don't really think any two patients really present in the exact same way and have the same course, and patients come through the door through various mechanisms, either through referrals from primary physicians, diagnosis sometimes within the hospital. Increasingly patient referrals, patients are advocates for themselves and their families are often advocates for themselves, and they will find centers of excellence because the reality is myelofibrosis and myeloproliferative neoplasms are rare diseases.”

How is myelofibrosis diagnosed?

“Myelofibrosis itself has to be diagnosed with a bone marrow biopsy, nowadays with mutational testing, chromosomal testing, and putting all of that together so that you meet certain World Health Organization criteria for either primary myelofibrosis or secondary myelofibrosis from an antecedent essential thrombocythemia or polycythemia vera.”

“So, getting the diagnosis is crucial because the treatments are tailored to the diagnosis and the subtypes of disease. Then I think making sure that your disease or the treatment plan for your disease is personalized and tailored to the goals of therapy for you because it really is, as I keep saying, it's variable. It's variable in how patients present their clinical course, and their treatment goals could be different.”

Mapping Myelofibrosis logo
Explore MappingMF.com for more information.

Trademarks are owned by or licensed to the GSK group of companies.

©2023 GSK or licensor.
MMLCOCO230009 May 2023
Produced in USA.


Myelofibrosis (MF) is a blood cancer characterized by the buildup of scar tissue in the bone marrow, which interferes with the production of healthy blood cells.

In the U.S., approximately 25,000 people are affected by MF.

MF is part of a bigger group of blood cancers called myeloproliferative neoplasms, or MPNs. MPNs affect the blood and bone marrow, which is the spongy tissue inside your bones. In people with MF, there is inflammation and scarring of the bone marrow, which is called fibrosis. This leads to abnormal production of blood cells.

There are different types of MPNs. Each has unique symptoms and different effects on the body.

Platelet count

Essential thrombocythemia (ET)

ET happens when your body makes too many platelets. Having high amounts of platelets in your blood can lead to blood clots and other complications.


Polycythemia vera (PV)

PV is a type of MPN that happens when the body primarily makes too many red blood cells.  Too many red blood cells can cause blood to thicken and move slower throughout the body. In some patients with PV, the body may also make too many white blood cells or platelets.



In people with MF, uncontrolled inflammation in the bone marrow can lead to scarring, which is known as bone marrow fibrosis. The inflammation and scarring lead to abnormal or ineffective production of blood cells by the bone marrow.

When MF happens on its own, it’s called primary MF. When MF develops because of another MPN such as PV or ET, it's called secondary MF. Secondary MF is sometimes called "post-PV MF" or "post-ET MF."


MF is a chronic disease, which means that it should be managed over time. By working with your healthcare team, you may be able to better navigate your symptoms.

Who is at Risk for Developing Myelofibrosis?

While anyone can be impacted by MF, certain risk factors can increase the chance that a person will develop MF, including:

AgeMF is most commonly diagnosed in people over the age of 60, but it can occur at a younger age.

Another Blood DisorderSome people may develop MF as a result of complications due to essential thrombocythemia or polycythemia vera.

Exposure to RadiationThose who are exposed to very high levels of radiation may be at an increased risk of developing MF.

JAK2 MutationAbout half of people with MF have a change in their DNA, called a mutation, in a gene called Janus kinase 2, or JAK2.

Overactive JAK ProteinsThe JAK2 gene tells your cells to make JAK proteins. In some people, these JAK proteins are too active, causing the body to make the wrong number of blood cells and creating inflammation, both of which can lead to MF.  Your healthcare team can partner with you to help you understand your MF.

Symptoms of Myelofibrosis

Explore the Signs & Symptoms

Learn More

Doctor with Patient

Arriving at a Diagnosis

Learn More