Essential thrombocythemia (ET)
- Is one of a related group of blood cancers known as “myeloproliferative neoplasms” (MPNs) in which cells in the bone marrow that produce the blood cells develop and function abnormally.
- Occasionally occurs in older children, but is mostly diagnosed in adult men and women.
What You Should Know
- Hematologists and oncologists are specialists who treat people who have ET or other types of blood cancer.
- ET does not generally shorten life expectancy. However, medical supervision is important to prevent or treat thrombosis, a serious complication that can affect vital organs such as the brain or the heart. Also, for untreated pregnant patients with ET, there is a risk to the survival of the fetus.
What You Should Do
- Talk with your doctor about your diagnostic tests and what the results mean
- Talk with your doctor about all your treatment options and the results you can expect from treatment.
- Ask your doctor whether a clinical trial is a good treatment option for you.
How Does ET Develop?
The DNA (genetic material) of a developing stem cell in the bone marrow is damaged. This is called an “acquired mutation.”
- Stem cells form blood cells (white cells, red cells and platelets).
The mutated cell leads to uncontrolled blood cell production, especially platelets - although red cells and white cells are usually affected as well.
- There is mainly an overproduction of platelet-forming cells, called "megakaryocytes," in the marrow.
This results in the release of too many platelets into the blood.
- The platelets’ function is to start the process of forming a plug (clot) in response to blood vessel injury in order to prevent or minimize bleeding. When platelets are present in very high numbers they may not function normally and may cause a blockage in blood vessels, known as a "thrombus." Less often, a high number of platelets can also cause bleeding problems.
Another word for platelet is "thrombocyte." The term "thrombocythemia" means an excess of platelets in the blood. The term "essential" indicates that the increase in platelets is an innate problem of the blood cell production in the bone marrow. "Secondary thrombocytosis" is the term for a condition that results in very high platelet counts in the blood in reaction to another problem in the patient's body, such as inflammatory disease, removal of the spleen, or iron deficiency in adults. A patient with secondary, or reactive, thrombocytosis should have a return to normal platelet count in the blood once the primary problem is treated successfully.
For most people who have essential thrombocythemia (ET), there are no obvious reasons (risk factors) why they developed the disease.
Doctors don't fully understand what causes ET. About half of all patients with ET have a mutation (change) of the JAK2 (Janus kinase 2) gene. This mutated gene may play a role in ET's onset. However, researchers are still studying its precise role as the cause of the disease.
Source: Essential Thrombocythemia. Reviewed by Srdan Verstovsek, MD, PhD.