Essential thrombocythemia (ET) is a malignant disease, one of the chronic myeloproliferative syndromes (CMPS), or myeloproliferative neoplasms, along with chronic myeloid leukaemia, polycythemia vera and primary myelofibrosis. These diseases have a common characteristic, the stem cells in the bone marrow, responsible for producing all the blood cells, have a defect which makes them produce one of the myeloid lineage blood cells in an uncontrolled manner.

In the case of ET, a mutation in the blood stem cell causes there to be a very high level of platelets. Platelets are tasked with starting the coagulation process in response to an injury of a blood vessel to keep bleeding to a minimum. When there are too many platelets, they may not function normally, and instead cause a blockage of the blood vessels, known as thrombosis.

In our country essential thrombocythemia is, together with chronic myeloid leukaemia, the most frequent CMPS. Its incidence is around 20 cases per million, per year and it predominantly affects patients of mature age (with an average age of 60), although 15% of patients are under the age of 40. There are some cases in children, and the disease affects women more frequently than men.

In many cases (more than 50%) it is a disease that does not present any symptoms, and is therefore often diagnosed by chance as a result of a routine blood test. If there are clinical manifestations they tend to be due to microcirculatory disorders (up to 40%) (reddening and pain in the fingers and toes, ischemia and distal extremity gangrene, transient ischemic attack, syncope, dizziness, visual alteration), thrombosis (up to 25%) (especially in arteries, much less frequently in veins), and hemorrhages (5%). Up to 35% of pregnant women with ET present miscarriage, maternal complications being infrequent.

The diagnosis of ET is based on fulfilment of all the following criteria: number of platelets greater 450,000 on a permanent basis; a bone marrow biopsy with a predominance of megakaryocytes (platelet precursors); absence of data to suggest another of the CMPS (diagnosis of exclusion); demonstration of a characteristic mutation in gene JAK2 or absence of causes of reactive thrombosis (such as iron deficiency, or absence of the spleen, amongst others).

Treatment for essential thrombocythemia depends on the age of the patient, the number of platelets, and whether the patient has a history of thrombosis or hemorrhages. At the present time there is considerable controversy about whether asymptomatic essential thrombocythemia patients need to receive treatment, or not. Most authors recommend treating only high-risk patients, patients over the age of 60, patients who have a history of thrombosis or hemorrhages, or with a platelet count in excess of 500,000.

The drugs most commonly used to treat such high-risk patients are hydroxyurea (for patients over the age of 60) and anagrelide or interferon alfa (for younger patients who do not tolerate hydroxyurea).

Low doses (100 mg/day) of acetylsalicylic acid (Aspirin) are indicated for all high-risk patients, or patients with symptoms of microcirculatory disorders.

Para más información de calidad sobre la trombocitemia esencial, puedes consultar las siguientes páginas web:

 

• Essential Thrombocythemia. Leukemia and Lymphoma Society

• Myeloproliferative neoplasms treatment. Leukemia and Lymphona Society
  
  
• Chronic myeloproliferative neoplasms treatment. National Cáncer Institute

There are other resources and links (in Spanish) of interest that may be of use to essential thrombocythemia patients

• Recomendaciones generales sobre la alimentación durante el tratamiento del cáncer. ICO