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The cause of Essential thrombocythemia is still unknown.


Many patients with essential thrombocythemia (ET) remain symptom-free for a long time.

The role of blood platelets

Blood platelets play an important role in the formation of blood clots. Symptoms of the disease can either be confirmed by a very high platelets count or, in other cases, by means of the functions they are performing. A high number of dysfunctional platelets circulating through the blood stream can lead to bleeding, while a high number of normal platelets increase the risk of blood clots.

Bleeding and impairment of the microcirculation

Bleeding occurs mostly in the form of nose and gum bleeding, but can also happen in the stomach and intestinal areas as well as through the skin.

When blood clots begin to form in the thinnest vessels, the supply of blood to the affected tissue will become restricted. This occurs in around half of the patients and is noticeable in the fingers and toes through a reddening of the skin, which is accompanied by swelling (erythromelalgia) and a burning and tingling sensation. In the central nervous system, it manifests itself in the guise of functional disturbances such as repetitive sight and speech disorders, dizziness, balance difficulties, paralysis and even seizures.

Possible complications 

The most common complications that arise with essential thrombocythemia are blood clots (thrombosis) in the venous or arterial system (infarctions).  They can occur in the large vessels of the upper abdomen (portal vein, hepatic veins, splenic veins, mesenteric veins) as well as in the coronary arteries and in the arteries that serve the brain.

The overall condition of the blood vessels also plays a decisive role in blood coagulation. Hence, the older the person the higher the risk.


Essential thrombocythemia is often diagnosed by chance after a routine blood test. Further analysis as follows:

Blood analysis

  • Permanent increase in thrombocyte count  > 450.000/μl
  • Platelet (thrombocytes) function may be either impaired or normal.
  • Bone marrow puncture
  • A bone marrow puncture is required in order to confirm the existence of the disease. 

Genetic analysis

Distinct acquired mutations in myeloproliferative diseases may be indicative for underlying afflictions. The Philadelphia chromosome abnormality with its shortened chromosome 22 is associated with chronic myelogenous leukemia. The JAK2 V617F gene mutation may be found in chronic myeloproliferative diseases such as polycythemia vera or essential thrombocythemia. Genetic testing is gaining increasingly widespread support due to its easily obtainable and precise diagnostic parameters that could also minimize the need for further invasive diagnostic procedures.

Ultrasound scan

An ultra sound scan can be used to assess hepatosplenomegaly, which can then provide an indication of how far the disease has progressed.

Video Interview with Dr. Claire Harrison

Dr. Claire Harrison talking about how and when ET is usually diagnosed, expectations for future therapies, recommendations to ET patients and what it means to live with a rare disease for patients and their relatives. 

Find out more in the video below:

Dr. Claire Harrison, MD, DM, FRCP, FRCP at the Guy's and St. Thomas' NHS Foundation Trust, London, UK