Essential thrombocythaemia (ET)
Essential thrombocythaemia (ET), is also known as primary thrombocythaemia. This is one of a group of conditions known as myeloproliferative diseases (MPDs).
Myeloproliferative diseases (MPDs)
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MPDs are a group of conditions that affect the way the bone marrow works. In MPDs the bone marrow makes too many of one or more types of blood cells.
The main types of MPD are:
Some people with essential thrombocythaemia develop myelofibrosis. This is a condition in which the bone marrow becomes scarred. Rarely, people with MPDs develop leukaemia.
The bone marrow is the spongy material in the centre of some of our bones. It makes cells known as stem cells. Stem cells are early blood cells that develop into three different types of blood cells:
red blood cells, which carry oxygen to all cells in the body
white blood cells, which fight infections and form part of our immune system
platelets, which help the blood clot to prevent bleeding.
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Essential thrombocythaemia is a rare condition affecting the bone marrow in which too many platelets are made.
It is a rare condition that can affect people at any age, including children, but it's most common in people over 50.
ET usually develops very slowly and for most people doesn't affect their normal life span.
Signs and symptoms of essential thrombocythaemia
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Having too many platelets in the blood may not cause any symptoms, and many people with ET are diagnosed during a routine blood test, when they have no symptoms.
Possible symptoms include:
redness, swelling or pain in the hands or feet due to reduced blood flow in these areas
Sometimes symptoms develop due to complications of ET, such as a blood clot or abnormal bleeding. Too many platelets in the blood can cause clots to form. Less commonly people may have abnormal bleeding because the platelets in their blood don't work properly.
Symptoms can occur because a blood clot (thrombosis) has formed in a vein in the body. Clotting problems are more common in people over 60, in people who have had a blood clot before, and in people who have conditions such as high blood pressure or diabetes.
Symptoms of a blood clot depend on where it is in the body. These are some common sites where a clot may form:
The deep veins of the leg – This can cause pain, swelling, heat and redness, especially in the calf. This is known as deep vein thrombosis or DVT.
The brain - This may cause mild symptoms such as headaches, blurred or double vision, or dizziness. Blood clots in the brain may also cause a stroke or mini stroke (also called a TIA). Symptoms of a stroke or TIA may include weakness, numbness or pins and needles in part of the body, or difficulties with speech or swallowing.
The heart - A blood clot in the heart may cause chest pain and in severe cases can result in a heart attack.
The lungs - A blood clot in a lung may cause breathlessness and chest pain. This is known as a pulmonary embolism.
This is a less common complication than blood clots. It can cause:
abnormal vaginal bleeding
Diagnosis of essential thrombocythaemia
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ET is usually diagnosed by a haematologist (a specialist in blood disorders). The diagnosis may be suspected after the results of a blood test called a full blood count (FBC). This test counts the number of red blood cells, white blood cells and platelets. In ET there will be a high platelet count.
Other conditions can cause an increase in platelet count, such as an infection, arthritis, chronic bleeding or a lack of iron in the blood. These need to be ruled out before a diagnosis of ET can be made.
Tests and investigations that may be done to confirm a diagnosis of ET are:
JAK2 blood test
JAK2 is a gene that is important in regulating blood cell production. If a change (mutation) happens in this gene, it can cause ET. About half of all people with ET have a mutation in the JAK2 gene. This change in the gene happens during the person's lifetime. It isn't something you’re born with and you can’t pass it onto your children.
Bone marrow sample (biopsy)
Your specialist may want to take a sample of marrow (biopsy) to be checked. The sample is usually taken from the back of your hip bone (pelvis). You’ll 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 (called a bone marrow aspirate) into a syringe.
After this, the doctor will take a small core 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 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.
Treatment for essential thrombocythaemia
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The aim of treatment is to reduce the risk of complications particularly blood clots. If treatment is successful, the outlook for someone with ET can be very similar to that of someone of the same age who doesn’t have the condition.
This is often used, as it can reduce the ability of platelets to ‘stick’ together. This doesn’t affect the platelet count, but can help lower the risk of blood clots. Side effects of aspirin include an increased risk of bleeding and ulcers in the stomach.
If you need to take a painkiller when you’re taking aspirin, ask your doctor what they advise. Some types of painkillers called NSAIDs (non-steroidal anti-inflammatory drugs), such as ibuprofen, may not be suitable for you.
Treatment to reduce platelet numbers (cytoreductive therapy)
If you have a lower risk of developing complications such as blood clots, you may not need treatment other than aspirin. You will be seen by your doctor who will monitor your condition with regular blood tests. If you are at high risk of blood clots, you’ll usually be started on treatment to reduce the numbers of platelets in your blood. This is called cytoreductive therapy.
This is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. It may be given to try to reduce the platelet count.
Hydroxycarbamide is the most commonly used chemotherapy drug to treat ET and is taken as a tablet. It can cause side effects, but generally these are mild. Side effects can include lowered resistance to infection, reduced red blood cell numbers (anaemia), diarrhoea or constipation.
Hydroxycarbamide may also 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. It's advisable to use effective contraception while taking the drug and also for a few months afterwards.
If hydroxycarbamide is used in combination with other chemotherapy drugs over a long period of time, it may increase the chance of the ET developing into a leukaemia.
The chemotherapy drug busulphan may also be used. Busulfan is usually given as a tablet, but it can be given as an injection into a vein. It can cause similar side effects to hydroxycarbamide.
Interferon is a protein that occurs naturally in the body. It can also be made as a medicine. It slows down the production of blood cells, including platelets. It’s most often used to treat ET in younger people (under 40), although it can be used at any age. Interferon is given as an injection under the skin. Possible side effects include flu-like symptoms, headaches, dizziness and tiredness.
This is a drug that reduces the number of platelets in the blood. It's taken as a capsule. Side effects can include headaches and palpitations (the sensation of a fast heartbeat).
It doesn't seem to affect fertility, but anagrelide should never be taken during pregnancy or if you are thinking of getting pregnant. It's important to use effective contraception when taking anagrelide.
Anagrelide is usually given when other treatments have already been tried. Some studies suggest it may increase the chance of changes in the bone marrow that may develop into myelofibrosis.
Radioactive phosphorus (32P)
This may be used to treat ET and is given as an injection into a vein. It irradiates the bone marrow and can lower the number of platelets being produced. The effects of a single injection can last from months to years.
Treatment with radioactive phosphorus over many years can cause an increased risk of leukaemia.
Your doctor or nurse will explain your treatment to you and answer any questions you have.
Clinical trials for essential thrombocythaemia
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New treatments for ET are being researched all the time. Your doctor may invite you to take part in a clinical trial to compare a new treatment against the best available standard treatment. Your doctor must discuss the treatment with you, and have your informed consent before entering you into a trial.
Before any trial is allowed to take place, it must be approved by a research ethics committee, which protects the interests of those taking part.
You may decide not to take part or to withdraw from the trial at any stage. You will then receive the best standard treatment available.
Monitoring for essential thrombocythaemia
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Your treatment may continue for a number of years, and you will need to have regular check-ups and blood tests. If you have any problems, or notice any new symptoms in between these times, let your nurse or doctor know as soon as possible.
Living with essential thrombocythaemia
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In addition to the treatments and check-ups recommended by your haematologist, you may want to look at additional ways of optimising your health and feeling the best you can. Things like following a healthy diet, drinking plenty of fluids, staying active and giving up smoking are good for your general health. These steps can also help reduce the risk complications such as blood clots. Your doctor or specialist nurse can give you information and support that fits your individual situation.
Everyone has their own way of dealing with their diagnosis and the different emotions they experience. Adjusting to the news that you have a long-term condition can take time, and it’s important that you get the support that you need. You may find it helpful to talk things over with family and friends or your doctor or nurse. You can also contact our cancer support specialists or the organisations below for more information and support.
Leukaemia CARE is a national group promoting the welfare of people with leukaemia and other blood disorders. Has regional support groups.
MPD Voice provides information and emotional support and fund research into MPDs.
This information has been compiled using information from a number of reliable sources, including:
Guideline for the investigation and management of adults and children presenting with a thrombocytosis. British Journal of Haematology. 2010. 149: 352–375.
Lee, et al. Wintrobe’s Clinical Haematology. 12th edition. 2009. Lippincott Williams and Wilkins.
Thanks to Dr Anne Parker, Consultant Haematologist, and the people affected by cancer who reviewed this edition.
Reviewing information is just one of the ways you could help when you join our Cancer Voices network.