The normal human platelet reference value is 100-300×10e9/L. When the platelet count is greater than 400×10e9/L, it is called thrombocythemia, which is mainly seen clinically in the following cases. I. Primary thrombocythemia. This disease is due to excessive proliferation of bone marrow caused by thrombocytosis. It is characterized by excessive proliferation of bone marrow megakaryocytes, persistent and significant increase of platelets in peripheral blood, and functional abnormalities, clinical tendency of spontaneous bleeding and or thrombosis, and patients often have splenomegaly. About 20% of patients, especially young patients, are asymptomatic. 1/3 of patients have headache, dizziness, blurred vision, burning pain in the palms and soles of the feet, and numbness at the end. 80% of patients have bleeding and thrombosis. Bleeding is common in the gastrointestinal tract, but may also include nasal and gingival bleeding, hematuria, aspiration bleeding, and skin and mucosal petechiae. 30% of patients have arterial or venous thrombosis. The splenic, mesenteric and lower limb veins are the most common sites of thrombosis. After lower limb vascular embolism, the limb may show numbness, pain, or even gangrene. It also shows erythematous limb pain and intermittent claudication. Mesenteric vascular thrombosis may cause vomiting and abdominal pain. Embolism in the lungs, kidneys, adrenal glands or brain can cause clinical symptoms and can be a cause of death. Splenomegaly is seen in more than 80% of cases and is usually mild to moderate, with a few patients having hepatomegaly. The platelet count is more than 600×10e9/L. The white blood cell count may be normal or increased, and a few patients may become anemic due to blood loss. Bone marrow is dominated by megakaryocyte hyperplasia. Half of the patients have positive JAK2 gene test. Other myeloproliferative disorders include chronic granulocytic leukemia, true erythroblastosis, primary myelofibrosis, etc., which may be accompanied by thrombocytosis. 1, chronic granulocytic leukemia patients with leukocytosis and splenomegaly are more obvious, peripheral blood and bone marrow are predominantly increased by middle and late juvenile granulocytes, rod-shaped nuclear granulocytes, positive Ph1 chromosome, or BCR-ABL. In addition to the above symptoms of primary thrombocytosis, true erythrocytosis is also characterized by purple-red skin and mucous membranes, hepatosplenomegaly, and elevated blood pressure in some patients, and positive JAK2 gene test in more than 80% of patients. More than 80% of patients have positive JAK2 gene test. 3. Primary myelofibrosis often has splenomegaly and anemia, peripheral blood has young granulocytes and teardrop red blood cells, bone marrow is often dry, bone marrow biopsy has fibrosis, and more than half of the patients have positive JAK2 gene test. Reactive (secondary) thrombocytosis Reactive thrombocytosis platelet count generally does not exceed 600×10e9/L, individual patients may occasionally exceed 1000×10e9/L, platelet function is basically normal, usually not accompanied by thrombosis and splenomegaly, platelets can return to normal after control of the primary disease or removal of the cause. 1, acute and chronic inflammatory diseases: acute inflammatory recovery, rheumatic fever, rheumatoid arthritis, periarteritis nodosa, ulcerative colitis, restrictive colitis, tuberculosis, nodular disease, chronic lung abscess, osteomyelitis, etc. 2, blood diseases: iron deficiency anemia, hemolytic anemia, acute or chronic blood loss. 3.Recovery period of thrombocytopenia (rebound thrombocytosis): such as the recovery period of blood cells after the myelosuppression period of chemotherapy, after the treatment of megaloblastic anemia, after the correction of alcoholism. 4.After splenectomy: half of the splenectomies have thrombocytosis within one week, and generally return to normal in two months. 5, malignant tumors: some solid tumors, lymphomas, etc. can be accompanied by thrombocytosis. 6, other: including trauma, after surgery, childbirth, after exercise, after the application of adrenaline. Therefore, if there is thrombocytosis, the cause and the original disease can be clarified only after the analysis of the comprehensive medical history, physical examination and relevant examination results.