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Myelofibrosis (PMF)

This page is about myelofibrosis. There is information about


What myelofibrosis is

Myelofibrosis is pronounced my-eh-lo-fy-bro-sis. It is a rare blood disorder. Myelo means bone marrow and fibrosis relates to the development of fibrous or scar tissue. So myelofibrosis is a condition that causes scarring of the bone marrow.

Myelofibrosis can develop without having had any other condition. This is called primary myelofibrosis (PMF) or chronic idiopathic myelofibrosis. It can also develop in people who have polycythaemia vera or thrombocythaemia. This is called secondary myelofibrosis.

The bone marrow is the soft inner part of our bones that makes blood cells. All blood cells start from the same type of cell called a stem cell. The stem cell makes immature blood cells. The immature cells go through various stages of development before they become fully developed blood cells and are released into the blood as

  • Red blood cells to carry oxygen around our bodies
  • White blood cells to fight infection
  • Platelets to help the blood clot

The diagram shows how the various different types of cells develop from a single blood stem cell.


In people with myelofibrosis the stem cells make too many megakaryocytes. These usually develop into megakaryoblasts and then platelets. Megakaryocytes also produce other cells called fibroblasts. Fibroblasts make a number of substances that help in wound healing and maintaining the body’s supportive tissue (connective tissue). These substances make scar tissue form in the bone marrow. The scar tissue crowds out the bone marrow and stops it working normally. Gradually the bone marrow produces fewer blood cells. As the number of new blood cells falls, the liver and spleen try to make more blood cells. But they aren’t as good at making them as the bone marrow and they become enlarged.

Myelofibrosis usually affects red blood cells first. The bone marrow keeps trying to produce more of them but they are often immature and tear drop shaped, which is abnormal. This means they are not able to work normally which causes anaemia. As myelofibrosis develops, the bone marrow also makes fewer white blood cells and platelets. Myelofibrosis can also cause an enlarged spleen (doctors call this splenomegaly).

Myelofibrosis is a type of myeloproliferative disorder. These are a group of blood conditions. We have a separate page about  myeloproliferative disorders.

Treatment controls myelofibrosis for many people for some time. How long treatment continues to work varies from person to person. It depends on a number of factors including your blood count at diagnosis, the symptoms you have and the number of immature cells you have in your blood. How the condition develops also varies. Some people develop more serious problems, such as heart disease and infections that may be difficult to control. Between 1 and 2 out of every 10 people diagnosed (10 to 20%) go on to develop an acute myeloid leukaemia.


Risks and causes

Researchers have found that around half of those who have myelofibrosis (50%) have a change in a gene called JAK2. The JAK2 gene makes a protein which controls how many blood cells the stem cells make. We need more research to find out what causes this change in the JAK2 gene.

There are a number of other gene changes that people with myelofibrosis may have, but they are much rarer.

About a third of those with myelofibrosis have a history of essential thrombocythaemia or polycythaemia vera.



Myelofibrosis usually develops slowly and doesn’t cause symptoms at first. Around a third of those diagnosed find out about it when having a blood test for something else.

As the condition progresses it causes symptoms. Most of the symptoms are linked to a fall in the number of blood cells

  • Tiredness and shortness of breath – due to low numbers of red blood cells
  • Bleeding and bruising easily – due to low numbers of platelets
  • Pain and discomfort in the abdomen due to enlarged spleen and liver
  • Bone pain
  • Gout
  • Loss of appetite and weight loss
  • Fever and night sweats

Tests to diagnose myelofibrosis

You will have a blood test to check your blood cell counts. Most people are anaemic but some people have a normal or increased haemoglobin. Many people have higher than normal white blood cell count and platelets at diagnosis but these usually drop as the disease progresses.

You will also have a bone marrow biopsy and an ultrasound of your spleen. The spleen is on the lefthand side of your tummy (abdomen).

If these tests suggest you have myelofibrosis you will then have another blood test to look for gene changes.


Your outlook

There are particular factors that doctors use to work out whether your myelofibrosis is low, medium or high risk to your health. This is called the International Prognostic Scoring System. There are 4 risk groups

  • Low risk
  • Intermediate 1
  • Intermediate 2
  • High risk

Your risk group depends on

  • Your white blood cell count – a high one is higher risk
  • Your haemoglobin – less than 10 is higher risk
  • The number of blasts (immature blood cells) in your blood
  • Your symptoms
  • Your age – if you are over 65 years you are higher risk

Low risk myelofibrosis can be kept under control for much more than 10 years in many people. In high risk myelofibrosis, survival may be months to a few years. Because the predicted outlook depends on so many different factors, it is best to discuss it with your own specialist, who has access to all your test results, and how they have changed over time.


Treatment for myelofibrosis

From looking at the scoring system, and finding your risk group, your doctor can decide on the best treatment for you. If you don’t have symptoms you may not need to have treatment. Instead you will have regular check ups including blood tests to check your blood count.

Your treatment will depend on the symptoms you have and your risk of developing problems.

Treatments may include one or more of the following

Blood transfusions

Blood transfusions increase the number of red blood cells. This helps to control tiredness, breathlessness and weakness.

You may also need to take folic acid tablets if you are very anaemic.


When red blood cells are broken down by the body they produce urea. Too much urea upsets the chemical balance in the blood and causes gout. Allopurinol reduces the amount of urea. You take it as a tablet.


Chemotherapy uses cell killing (cytotoxic) drugs to destroy the immature cells. The drugs work by disrupting the growth of cells and stopping them from dividing. They can help to reduce enlargement of the spleen and liver. Chemotherapy is not suitable for everyone because one of the side effects is the lowering of the number of blood cells. The drugs doctors use may include

The links above will take you to more information about each drug and its side effects.

Androgen therapy

Androgens are hormones made by the adrenal gland. Doctors use them to help to control anaemia. You take them as a tablet. There are a number of different types including danazol. Androgens have side effects including an increase in body hair and sexual desire and retention of fluid. They can also cause changes in your liver and cause prostate cancer. Men will have screening for prostate cancer.


If your spleen is enlarged and other treatments are not working to reduce its size, you may need to have an operation to remove your spleen (splenectomy). The operation does have risks for someone with myelofibrosis. These include infection, bleeding and development of blood clots, which can become serious. So it is not a suitable treatment for everyone.


Radiotherapy is the use of high energy X-rays to kill cells. If your spleen is enlarged and you are unable to have surgery, your doctor may suggest you have radiotherapy. This helps to reduce the size of your spleen. But it usually only controls symptoms for a few months.

Donor cell transplant

To have a donor stem cell transplant you first have to have your own bone marrow cells destroyed. This means having high dose chemotherapy. You may also have total body radiotherapy. These treatments destroy the cells in your bone marrow.

After this treatment you have stem cells from a donor to replace your own bone marrow cells. You have these through a drip into your bloodstream. Usually this is through a central line rather than through a drip into your arm. To be able to have intensive treatment you need a stem cell donor. The donor is someone whose stem cells match yours. The most suitable donor is usually a close relative such as a brother or sister. If you do not have a suitable family donor your doctor may look for an unrelated donor for you (through registers like Anthony Nolan).

It takes from a few days to a few weeks for the donor stem cells to start making new blood cells. During this time you will need blood and platelet transfusions and are at a high risk of developing infections. So your doctor and nurses will give you antibiotics and anti viral drugs to try to prevent them. You can read more about stem cell transplants in the cancer treatment section.

This treatment is very intense and has risks. You can only usually have this if you

  • Are younger
  • Are in reasonably good health, apart from your myelofibrosis
  • Have a suitable donor (sibling or unrelated)

Biological therapy

Biological therapies are treatments developed from natural body substances or that change how cancer cells signal to each other. They can slow or stop the growth of cancer cells. 

For myelofibrosis, researchers are looking into new types of biological therapy treatment that stop the JAK2 gene signalling to stem cells to make blood cells. These drugs are called JAK2 inhibitors. In 2 trials in the US that reported in 2012, a JAK2 inhibitor called ruxolitinib helped people with myelofibrosis. It reduced spleen size, reduced symptoms and helped people to live longer. This treatment has not been approved by the National Institute for Health and Care Excellence (NICE) and so is not standard treatment within the NHS in the England and Wales. The Scottish Medicines Consortium (SMC)  has recommended ruxolitinib for people with myelofibrosis in Scotland. Research is continuing to try to find out how best to use ruxolitinib.



Researchers are looking into how myeloproliferative disorders develop. Some of this research is suggesting that it may be better to group them depending on whether they are JAK2 positive or negative rather than on the type of myeloproliferative disorder. We need more research to find the best way to group these conditions and what the best treatment is.

There is also research into new treatments for myelofibrosis. Thalidomide and lenalidomide are drugs that interfere with how cells signal to one another and stop the development of blood vessels. Blood vessels develop in the bone marrow with myelofibrosis. Reducing their development may help the bone marrow produce more normal red blood cells.

Early research is also looking into a new type of biological therapy called ruxolitinib or INC424. Ruxolitinib stops signals that cancer cells use to grow and divide. There is currently a trial looking at ruxolitinib and BKM120 for myelofibrosis. BKM120 is also a type of biological therapy.

Another early trial is looking at ruxolitinib with panobinostat for myelofibrosis. Panobinostat is another type of biological therapy. It works by blocking enzymes that cells need to grow and divide.

Another trial is looking at ruxolitinib and LDE225 for myelofibrosis. LDE225 is a new drug that blocks a specific type of cell signalling called the hedgehog pathway. The aim of this trial is to find the highest safe doses of ruxolitinib and LDE225 that you can have at the same time, and to see if having both drugs helps with myelofibrosis.

 The MPD-RC114 trial is looking at ruxolitinib before a stem cell transplant.

The PERSIST-1 trial is comparing a biological therapy drug called pacritinib with other available treatments for myelofibrosis. Pacritinib is a type of cancer growth blocker. This trial has now closed and we are waiting for the results.


Coping with myelofibrosis

Coping with a rare condition can be difficult both practically and emotionally. Being well informed about your condition and possible treatments can make it easier to make decisions and cope with what happens.

It can also help to talk to people with the same thing. But it can be hard to find someone with a rare condition. Check out Cancer Chat – Cancer Research UK’s discussion forum. It is a place to share experiences, stories and information with other people who know what you are going through.

There are also a number of organisations that offer help and support

MPD Voice
They offer information and support to people with myeloproliferative disorders.

Leukaemia Care
They offer information and support to people with leaukaemia and related blood conditions and have a message board.

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Updated: 25 February 2014