Essential Thrombocythemia (ET)

Symptoms and Causes

ET occurs when your bone marrow makes too many platelets – substances that help your blood clot – and the blood platelet count is persistently elevated.

Mostly people between the age of 50 and 70, although it sometimes affects younger people. It occurs more frequently in women than men.

In blood and bone marrow tests for ET, doctors look for a persistently raised platelet count. Normal platelet counts vary between 150,000 and 400,000 per microliter of blood but in ET, the count can be many times higher.Your doctor will rule out other causes of a raised platelet count, and then send you for further tests, including a bone marrow examination and a gene mutation test. Once your diagnosis is confirmed, your doctor might recommend further blood tests to check your health and work out how well organs such as your liver and kidneys are functioning.

As your bone marrow makes too many platelets, you’re at higher risk of having a blood clot (or thrombosis) that blocks a vein or an artery, potentially causing a stroke or heart attack; too many white blood cells have been linked with increased risk of thrombosis too. You might also have a higher risk of excess bleeding.As a result of these changes in your blood, some of the other common symptoms of ET include:

  • Persistent or repeated headaches or migraines
  • Visual problems
  • Lightheadedness and dizziness
  • Skin itchiness (also called pruritus) or other unusual skin sensations
  • Abnormal bleeding, including: frequent or severe nosebleeds, frequent or severe gum bleeds, heavy menstrual periods, prolonged bleeding from minor cuts or injury, bruising for no apparent reason
  • Blockages in the smaller blood vessels in the fingers and toes, leading to symptoms including: tingling, burning or throbbing sensation in the hands and feet, skin redness on the hands and feet, cold or blue fingers and toes

One study asked 304 patients with ET about their most significant symptoms, with the results showing that 72% had fatigue as a symptom, followed by night sweats and bone pain, both reported by 41%. Other symptoms were itching (40%), fever (9%), spleen pain (9%) and weight loss (7%).

The cause of ET is unknown.

However, it has recently been discovered that mutations can alter the activity of signalling pathways. About 50% of people with ET have a change (mutation) in a protein known as JAK2 (short for Janus kinase) that regulates blood cell production. Mutations in the MPL gene are seen in about 5% of people with ET and about 30% have a mutation in the CALR gene.

People are not born with these mutations but acquire them during their lives. There is a rare form of ET that is inherited, likely caused by a genetic mutation, resulting in people in some families developing the disease more readily than others.

If you don’t have symptoms, your doctor might be happy to just monitor you for a period of time. You’ll have regular check-ups and blood count tests to check the progression of your condition. You might be monitored in this way for a long time.

More information about the management of ET can be found Click here

ET is regarded as incurable, however, in people who receive treatment, the disease can remain stable for long periods of time. Rarely, ET can change into myelofibrosis (MF, post-essential thrombocythemia myelofibrosis, or post-ET MF). There is a relatively low risk (<1%) of ET transforming into myeloid leukemia.