Myelofibrosis (MF) (or primary myelofibrosis) is one of a group of conditions known as myeloproliferative disorders (MPDs). These disorders affect how the bone marrow works.
The main types of MPD are:
Bone marrow is part of the immune system, which protects us from infection and disease. The marrow is in the spongy material found inside bones. This is where stem cells are made. Stem cells are blood cells at their earliest stage of development. All blood cells grow from stem cells. The bone marrow makes millions of blood cells every day. The three main types of blood cells are:
red blood cells – which carry oxygen around the body
white blood cells – which fight infections
platelets – which help blood to clot to prevent bleeding.
Myelofibrosis is a rare condition that affects the bone marrow. In MF, scar tissue builds up inside the bone marrow and blood cells aren’t made properly. It can affect people at any age, including children, but it's most common in people over 50.
MF can occur in people who haven’t any history of problems with their bone marrow. This is called primary myelofibrosis. MF can also develop in people who have essential thrombocythaemia (ET) or polycythaemia vera (PV). This is called post-ET myelofibrosis or post-PV myelofibrosis.
These are all called myelofibrosis as they behave in the same way.
People with MF may have low levels of one or more types of blood cells. If the bone marrow becomes scarred (fibrosed), it may make fewer blood cells. Some people have too few of some types of blood cells and too many of another type.
To make up for fewer blood cells being made in the bone marrow, other parts of the body, usually the spleen and liver, begin to make blood cells. As the spleen begins to make blood cells, it grows in size.
The enlarged spleen may ‘hold on’ to blood cells, instead of releasing them into the blood. The spleen may also destroy blood cells. This can reduce the numbers of blood cells in the blood.
Signs and symptoms of MF
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At first, MF may not cause any symptoms. Some people are diagnosed with MF when they have a blood test taken for another reason. When symptoms do develop, they are most often due to having too few blood cells or an enlarged spleen.
Possible symptoms include;
Sometimes other symptoms develop, such as gout (inflammation in the joints). This is due to complications that MF can cause.
Bleeding or bruising
Very occasionally MF can cause abnormal bleeding. This can cause symptoms such as:
abnormal vaginal bleeding
The spleen sits on the left side of the tummy (abdomen) just under the ribs and is normally about the size of a fist. It is involved in breaking down red blood cells. MF can cause the spleen to grow bigger than normal. Symptoms of an enlarged spleen include discomfort on the left side of the tummy and quickly feeling full when eating.
MF is usually diagnosed by a haematologist (a specialist in blood disorders). The diagnosis may be suspected from the results of a routine blood test called a full blood count. This test counts the number of red blood cells, white blood cells and platelets in the blood.
Tests and investigations that may be done to confirm a diagnosis of MF include:
This blood test checks for a change (mutation) in a gene called JAK2. This gene helps control how many blood cells are made. A change (mutation) in the gene, which happens during the person's lifetime, can cause MF. It isn't something you’re born with and you can’t pass it on to your children.
CALR blood test
Blood tests might also check for a change in another gene called calreticulin (CALR). As with the JAK2 gene change, it happens during the person's lifetime. It isn't something you’re born with and you can’t pass it on to your children.
Bone marrow sample (biopsy)
Your doctor may want to take a sample of bone marrow (biopsy) to examine under a microscope (see diagram below). The sample is usually taken from the back of your hip bone (pelvis). You will be given an injection of local anaesthetic to numb the area. The doctor will then pass a needle through the skin into the bone, and draw a small sample of liquid marrow (bone marrow aspirate) into a syringe.
After this, the doctor will also take a small core (piece) of marrow from the bone (a trephine biopsy). Both samples will be looked at later under a microscope.
The test can be done on the ward or in the outpatients department. The whole procedure takes about 15-20 minutes. It may be uncomfortable when the marrow is drawn into the syringe, but this should only last for a few seconds.
You may feel bruised and have an ache for a few days after the test. This can be eased with mild painkillers.
Sometimes, in the early stages of MF, not all of the bone marrow is affected. Because of this some people need to have a second bone marrow biopsy taken if the first samples look normal but their doctor still suspects MF.
Other tests and investigations may also be done, such as scans and x-rays. Your doctor or nurse will explain these to you.
Treatment of MF aims to control any symptoms you have. If you don’t have symptoms you may not need any treatment for a while. In this case, your haematologist will monitor your condition regularly. If you develop any symptoms between appointments, let your specialist know.
If you do have symptoms there are different treatments that may be used, but they're not all suitable for everyone. Your haematologist will talk to you about this.
If you have symptoms caused by a low red blood cell count (anaemia), you can be given blood transfusions. Usually it is possible to have a blood transfusion as a day patient, but it may involve an overnight stay in hospital. You can have blood transfusions as often as necessary.
Chemotherapy is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. It may be used to treat MF if the symptoms are severe.
Chemotherapy can help reduce the size of the spleen and the liver, and can help control other symptoms. It may also help increase the number of blood cells.
Hydroxycarbamide is the most commonly used chemotherapy drug to treat MF. It is taken as a capsule or tablet. It can cause side effects, but these are generally mild. Side effects can include being more at risk of getting an infection, having a reduced number of red blood cells (anaemia), diarrhoea or constipation.
There is a very small risk of leukaemia developing if hydroxycarbamide is used for a long time. People with MF who are under 40 may be given other drugs instead.
Chemotherapy isn't suitable for everyone with MF. It temporarily affects the way the bone marrow works and may reduce the level of blood cells, so if you have chemotherapy you'll be monitored very closely. Sometimes a smaller dose of chemotherapy is given to lower the risk of serious side effects. Your doctor or nurse will explain the possible side effects of any chemotherapy they recommend for you.
Chemotherapy may affect fertility. People taking it are advised not to get pregnant or father a child, as there may be a risk of harming the developing baby. Contraception should be used while taking the drug and also for a few months afterwards.
Thalidomide is a type of targeted therapy used to treat MF. It can be given on its own or in combination with steroid tablets. Thalidomide is taken as a tablet. The side effects can include feeling tired or drowsy, constipation and numbness or tingling of the hands and feet . If you feel drowsy it’s important not to drive.
Thalidomide can cause birth defects, so it should not be given to pregnant women. People taking thalidomide who are sexually active should use a barrier form of contraception.
JAK inhibitiors such as ruxolitinib (Jakafi ®) are a new type of treatment. They work by blocking (inhibiting) the faulty JAK2 gene. They may be suitable for some people with severe symptoms related to myelofibrosis or an enlarged spleen.
This is a drug that may be given to help improve anaemia (low number of red blood cells).
Erythropoietins are another treatment that may help to increase the levels of red blood cells in some people.
Steroids may sometimes be used to treat low levels of red blood cells.
Interferon is a natural substance made by the body. It can also be made as a medicine. It slows down the production of blood cells, including platelets. Interferon is given as an injection under the skin. Possible side effects include flu-like symptoms, headaches, dizziness, mood swings and tiredness.
Removing the spleen (splenectomy)
If your spleen is enlarged and causing symptoms, your specialist may suggest that you have an operation to remove it.
There can be advantages and disadvantages to having this operation. Your specialist will discuss these with you before you make a decision.
If it isn’t possible to remove the spleen it may be possible to shrink it using radiotherapy. Radiotherapy is the use of high-energy rays to destroy cancer cells, while doing as little harm as possible to the healthy cells. Radiotherapy can help improve symptoms such as pain and a high platelet count. But this improvement may only last for a few months.
Radiotherapy can cause temporary side effects, such as tiredness and skin irritation, although generally these are mild.
Stem cell or bone marrow transplant (from a donor)
Rarely, this intensive treatment is used for people with myelofibrosis. It involves giving high doses of chemotherapy, and then replacing stem cells (early blood cells) that have been destroyed by the treatment. After chemotherapy, you are given stem cells from a donor who can be a brother, sister or an unrelated donor who is a match for you.
Some people may have less intense doses of chemotherapy to weaken their immune system enough to allow the donor stem cells to grow in their bone marrow. This called reduced intensity conditioning.
Your doctor or nurse will explain your treatment to you and should answer any questions that you have.
There are also some newer treatments available, which may be used to help to control MF.
You may be invited to join a clinical trial looking at new ways of treating MF. You can talk about this with your haematology doctor.
You will need to have regular check-ups and blood tests. If you have any problems, or notice any new symptoms in between these appointments, let your nurse or doctor know as soon as possible.
You may have many different emotions including anger and resentment, guilt, anxiety and fear. These are all normal reactions, and are part of the process many people go through in trying to come to terms with their condition.
Everyone has their own way of coping with difficult situations. Some people find it helpful to talk to family or friends, while others prefer to seek help from people outside their situation. Some people prefer to keep their feelings to themselves. There is no right or wrong way to cope, but help is there if you need it. Our cancer support specialists can give you information about counselling in your area.
MPD Voice is a support network for people with MPDs (myeloproliferative disorders), providing information and support.
Leukaemia CARE is a national group promoting the welfare of people with leukaemia and other blood disorders. It has many regional support groups.
This information has been compiled using information from a number of reliable sources, including:
Reilly J, et al. Guideline for the diagnosis and management of myelofibrosis. British Journal of Haematology. 2012. 158: 453-471.
Ansell SM (Ed.) Rare Hematological Malignancies. 2008. Springer, New York.
With thanks to Dr Jyoti Nangalia, Clinical Research Fellow, who reviewed this edition.
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