Patients with Essential Thrombocythaemia (ET) - sometimes called Primary Thrombocytosis (PT) - have an elevated platelet count. Their blood contains too many platelets, and these excess platelets made the blood more ‘sticky’.

Some people with ET suffer from bleeding or clotting problems, while some have no symptoms at all.

People generally develop ET as adults; it's uncommon to inherit the disorder. Most are diagnosed with ET at age sixty or above, but unfortunately the disorder seems to be becoming more common in people under age forty, especially women.

Recent research has shown that about 50% of patients have a mutation in a protein called JAK2 - a protein that regulates blood cell production. This mutation may result from viral infections or radiation damage, but more research needs to be done to determine the causes of ET.

Next: Tests and diagnosis of ET