Essential thrombocythemia (ET) is a subtype of classic myeloproliferative neoplasm; it is characterized by a marked increase in peripheral blood platelet counts and an exuberant proliferation of megakaryocytes in the bone marrow. The clinical manifestation is a significant increase in platelets, often accompanied by bleeding and thrombosis. Thrombosis and hemorrhage are the most important complications in ET patients and seriously affect their quality of life and long-term survival. Very few ET patients have disease transformation to myelofibrosis or leukemia. In 2005, it was found that 50% of ET patients had JAK2V617F mutation and 5% had MPL mutation. Although clinical studies have been conducted in recent years in the United States and other countries to target JAK2 inhibitors for the treatment of ET patients with JAK2V617F mutations, some efficacy was obtained, but no molecular remission was achieved. At present, the treatment of ET is still based on hydroxyurea, anagrelide, interferon to reduce the platelet count and aspirin antiplatelet therapy. Clinical trials of anagrelide are underway in China. Among them, interferon treatment for ET has a remission rate of up to 80%, can result in spleen shrinkage, and only interferon treatment can reduce JAK2V617F gene load, which may enable patients to achieve molecular remission. Department of Hematology, Xuanwu Hospital, Capital Medical University, Huizhou, China I. Diagnosis of ET (a) Diagnosis of ET 1. 2008 WHO diagnostic criteria for primary thrombocythemia. The diagnosis requires meeting all 4 criteria. ① platelet count >450×109/L persistently; ② bone marrow examination is mainly megakaryocytic lineage hyperplasia with an increase in the number of mature large megakaryocytes, without obvious granulocytic or red lineage hyperplasia; ③ chronic granulocytic leukemia, true erythrocytosis, primary myelofibrosis, myelodysplastic syndrome or other myeloid tumors that do not meet WHO diagnostic criteria; ④ JAK2 V617F gene mutation or expression of other clonal markers, or absence of JAKV617F gene mutation without evidence of reactive thrombocytosis (including iron deficiency, splenectomy, surgery, infection, inflammation, connective tissue disease, metastatic cancer, lymphoproliferative disorders, etc.). (ii) Laboratory tests required for initial clinic routine blood, biochemistry, serum iron, ferritin, CRP, autoantibody profile, tumor screening, bone marrow aspiration, bone marrow biopsy, chromosome examination, stem cell culture, BCR-ABL gene test, quantitative JAK2V617 gene mutation test, abdominal ultrasound II. ET treatment (i) Risk stratification High risk: age > 60 years or presence of ET-related Thrombosis, bleeding or platelets >1500×109/L Intermediate risk: age 40-60 years, no high-risk factors Low risk: age <40 years, no high-risk factors (II) Treatment 1. Patients with ET should be screened for hypertension, hyperlipidemia, diabetes and history of smoking, and treated accordingly. 2. Unless contraindicated, all ET patients should be given aspirin therapy. 3.The aim of treatment is to bring the platelet count back to normal. 4. High-risk group: perform cytoreductive therapy and the first-line regimen for treatment is hydroxyurea + aspirin. Young or pregnant patients opt for interferon therapy. 5. Low- and intermediate-risk group: Undergo reduced-cell therapy in clinical trials or in patients with symptomatic ET (progressive splenomegaly, or severe microvascular symptoms that do not improve with aspirin, or uncontrollable bleeding due to elevated platelet counts). 6. Patients with uncontrollable cardiovascular risk factors are considered for decellular therapy. 7. Drug selection Age group First-line regimen Second-line regimen <40 years Interferon Anagrelide, Hydroxyurea 40-75 years Hydroxyurea Anagrelide, Interferon >75 years Hydroxyurea Anagrelide, Marilan