Essential thrombocythemia (throm-bo-sigh-THEE-me-uh), also called ET, is a stem cell disease. Your bone marrow produces stem cells, which include red and white blood cells as well as platelets needed for your blood to clot. ET causes the bone marrow to produce too many platelets and in some cases, too many white blood cells.
Although there isn't a cure for ET, reducing the number of platelets can help some people who develop symptoms. ET is one of several myeloproliferative disorders — a group of diseases in which the bone marrow makes too many red or white blood cells or too many platelets.
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