Essential Thrombocythemia (ET) is a chronic myeloproliferative neoplasm (MPN) characterized by an increased number of platelets in the blood. This blood cancer is commonly diagnosed at the age of 60, predominately in women. It is also found in younger people as well, as was the case with our daughter and several other young patients we came to know. ET creates a proliferation of platelet precursors in the bone marrow, and its most common complications include tendencies toward blood clotting and/or bleeding; later but more rare consequences include a transformation to myelofibrosis (bone marrow scarring) or acute leukemia.
Many patients are asymptomatic, diagnosed after blood counts as part of a routine check-up reveal a high platelet count. When symptoms are present, they may include fatigue, or may be related to small or large vessel disturbances or bleeding.
Small vessel disturbances (often considered vasomotor in nature) can lead to:
• Vision disturbances or silent migraines
• Dizziness or lightheadedness
• Coldness or blueness of fingers or toes
• Burning, redness, and pain in the hands and feet
Thrombotic complications can be quite serious, leading to:
• Transient ischemic attack (TIA)
• Heart attack
• Deep vein thrombosis or Pulmonary Embolisms (blood clots in the lung)
Bleeding can manifest as:
• Easy bruising, nosebleeds or heavy periods
• Gastrointestinal bleeding or blood in the urine
Uncontrolled ET can result in difficulties with pregnancy, including miscarriage, fetal growth changes, premature delivery, and placental abruption. It can also restrict blood flow to vital organs.
No one knows exactly what triggers the start of essential thrombocythemia (ET) or the other myeloproliferative neoplasms (MPNs). Recently, researchers discovered three acquired mutations that alter the activity of proteins that control signaling pathways in many patients with MPNs. Signaling pathways are important regulators of cell growth and development.
About half of all people with Essential Thrombocythemia have a mutation called "JAK2V617F" (found in the JAK2 gene) within their blood-forming cells. This mutation leads to hyperactive JAK (Janus kinase) signaling and leads to many of the characteristic features of the disease. The end result is that the body makes the wrong number of blood cells.
About 23.5% of people with myelofibrosis and ET have a mutation called Calreticulin, or CALR. This genetic marker was discovered in 2013 by two independent laboratories, including one funded by MPN Research Foundation and Friends of ET Research.
A third mutation is the MPL mutation that is found in some ET patients. Surprisingly, some ET patients are "triple-negative," meaning they don't have either of these known mutations.
Some epidemiological risk factors associated with ET include the following:
• Gender -- Women are 1.5 times more likely than men to develop the condition
• Age -- People older than 60 are most likely to develop the condition, although 20% of those with this condition are under 40
• Environment – Exposure to chemicals or to electrical wiring may increase an individual's risk for the condition.
The estimated prevalence for people living with ET in the US is between 75,000 (NIH) and 135,000 in any given year (MPN Research Foundation.) The National Organization for Rare Disorders classifies ET as a rare disease.
Acknowledgements and References:
National Institutes of Health