Background Essential thrombocythemia is a chronic myeloproliferative disorder; patients with this disorder have a propensity to develop thrombosis, myelofibrosis, and leukemia.Design and Methods We studied 605 patients with essential thrombocythemia (follow-up 4596 person-years) with the aim of defining prognostic factors for thrombosis, myelofibrosis, and leukemia during follow-up.Results Sixty-six patients (11%) developed thrombosis with a 10-year risk of 14%. Age >60 years (p60 years (p
