• What is ET?
  ET is a blood disorder in which the bone marrow in our bodies increases the platelet count. Some people suffer with bleeding or clotting, but some have no symptoms at all.
  
  
• What causes ET?
  The cause of ET is unknown, but damage to the bone marrow from viral infections or radiation may play a role. About half of patients with ET have a mutation (or change) in a molecule called JAK2 that occurs in blood cells. It is uncommon to inherit ET.
  
  
• What is the average age of someone being diagnosed with ET?
  ET usually occurs in people who are over 60 years old, but recently it appears to be becoming more common in people less than 40, especially women.
  
  
• How is it diagnosed?
  The diagnosis of ET includes finding a high platelet count and excluding causes of a reactive thrombocytosis (see below) and other bone marrow disorders. Your haematologist will examine any symptoms you may have as well as performing tests such as:
         
  • Blood tests including the test for JAK2 mutation
  • Chest x-ray
  • Ultrasound scan
  • Bone marrow test
    
    
• What is a Reactive Thrombocytosis?
  A Reactive Thrombocytosis occurs when your platelets are shown to be raised on a blood test, but this increase is not due to a long-term blood disorder. Causes of an RT include:
  • Infection (acute and chronic)
  • Inflammatory disorders
  • Acute and chronic blood loss
  • Tissue damage from trauma or surgery
  • Drugs (steroids, vincristine)
  • Chemotherapy
  • Splenectomy and hyposplenism
  • Malignancy, following damage to tissues
    
    
• What is bone marrow?
  Bone marrow is a spongy substance that runs along the inside of your long bones and acts as a "factory" for making blood cells. By looking at a sample of your marrow under the microscope, your haematologist will get a good picture of your blood-making mechanism.
  
  
• What is involved in a bone marrow test?
  Your doctor with usually take a sample of the bone marrow from the back of your pelvis bone. You will generally be asked to lie on your side with your legs curled up.

The area where the sample is to be taken will be cleaned and numbed by an injection of local anaesthetic - this can sometimes cause a stinging sensation which only lasts a few seconds. The doctor will insert a needle into the anaesthetised area.  You may feel a slight "pulling" sensation as the sample is taken.

For some people, a second sample called a trephine biopsy is required. This involves collecting a "core" of the bone. At this time you may feel an uncomfortable pushing sensation, but it will only last a few moments.

The whole procedure usually takes 20-30 minutes. The site will be covered with a small dressing and you will be asked to lie on your back for a few minutes.

The dressing needs to stay in place for 24 hours and it is best to avoid soaking in the bath during this time. You may experience slight discomfort in the area as the local anaesthetic wears off, which can be helped by taking a simple painkiller such as paracetamol.

• What are the possible complications of ET?
  People with ET are at high risk of blood clots (thrombosis) and bleeding (haemorrhagic) events. The chance of both bleeding and clotting complications of ET can be lessened with medication that reduces platelet stickiness and lowers the platelet count.

Long-term, less common complications include developing acute myeloid leukaemia or myelofibrosis. Some of the drugs used in treating ET may increase the risk of developing acute leukaemia.

• Can ET be passed down to my children?
  There is only a slim probability of this happening. It is more likely not to be passed down.
  
  
• Are there any other names for this condition?
  Essential thrombocytosis, thrombocytosis, primary thrombocythaemia (PT), primary thrombocytosis.
  
  
• What if I have ET and become pregnant?
  It is really important to discuss any plans of pregnancy with your haematologist, whether you are a man or woman. Some drugs used can be toxic to sperm or to an unborn baby. There can be a higher chance of thrombosis (blood clot) in pregnancy, and there is further risk with an addition of an ET diagnosis. The pregnant woman with ET can be more at risk of miscarriage, and there may be risk of growth problems in the later stages of pregnancy. Although the platelet count will reduce during pregnancy, interferon alpha is considered safe at this time and would be used if the platelet count was especially high, or where there is a history of thrombosis or other complications in your current or previous pregnancies. The doctor will probably prescribe low dose aspirin throughout pregnancy and heparin injections after the birth of your baby and sometimes during pregnancy.
  
  
• What is the prognosis?
  The prognosis depends on your complications, which may also affect your quality of life. In the absence of severe clotting (thrombotic) or bleeding (haemorrhagic) complications, you can expect a near normal life span. The onset of acute myeloid leukaemia or myelofibrosis (which can happen in a small proportion of cases after 10-15 years) can have a less positive outlook. This can be discussed with your doctor.
  

If you'd like to read more detailed information about essential thrombocythaemia (ET), please go to the ET main page