（Leukemia is a malignant tumor of the blood system, which is caused by the evolution of some cells in the hematopoietic stem cells, forming a “malignant clone”, from which differentiated leukemic cells, stagnate at a certain stage of cell development, and proliferate, do not follow the program of aging death, the formation of a large number of such leukemic cells occupy As a result, the normal hematopoietic function is inhibited, resulting in a significant reduction of normal blood cells produced by the bone marrow, which leads to a series of clinical manifestations such as anemia, infection, bleeding and infiltration of various organs. The cause of hematopoietic stem cell malignancy is often due to certain factors that lead to chromosomal deletions, translocations, aneuploidy and other changes, often forming new “fusion genes”, the proteins encoded by these fusion genes have certain abnormal functions, such as serving as some kind of signal to order a certain stage of hematopoietic cells to proliferate in large numbers, not according to the program of aging The proteins encoded by these fusion genes have certain abnormal functions, such as acting as signals to order a certain stage of hematopoietic cell proliferation, unprogrammed senescence (apoptosis), and thus the formation of leukemic cells. Many forms of chromosomal abnormalities and dozens of fusion gene types have been identified that can be used as a basis for diagnosis and to help determine prognosis, and have been or will be targets for treatment. Factors that contribute to abnormal chromosomal alterations include viral infections, ionizing radiation, chemical drugs and toxins, and genetic factors. Although many factors are thought to be associated with the development of leukemia, the exact cause of human leukemia is still unknown. According to foreign statistics, leukemia accounts for about 3% of the total incidence of tumors and is the most common type of malignancy among children and young adults. The incidence of leukemia is highest in Europe and North America, and lower in Asia and South America, and the incidence of leukemia in China is 2.76/100,000 per year. According to the stage of differentiation arrest and the natural course of leukemia cells, leukemia can be divided into two categories: acute and chronic; according to the different sources of leukemia cells, leukemia can be divided into two categories: myeloid leukemia and lymphocytic leukemia, so combining these two classifications, leukemia can be divided into four types, namely acute myeloid leukemia, acute lymphocytic leukemia, chronic myeloid leukemia and chronic lymphocytic leukemia. （Clinical manifestations of acute leukemia 1. fever: most of the fever is caused by infection, most commonly oral, perianal and pulmonary infections. 2. Bleeding: Early bleeding from the skin and mucous membranes may occur, and in severe cases, bleeding from internal organs. 3. Anemia: It is progressively aggravated and the symptoms of anemia are similar to those caused by other causes. 4. Manifestations of leukemic cell infiltration: enlargement of lymph nodes, liver and spleen, and sternal pressure pain. There may also be pleural effusion, peritoneal effusion or pericardial effusion, as well as central nervous system infiltration (headache, nausea, vomiting and other manifestations of increased intracranial pressure) and testicular infiltration. Some types of leukemia may present with gingival hyperplasia. Chronic leukemia progresses more slowly, and patients have no obvious symptoms in the early stage. As the disease progresses, leukemia cells destroy the normal hematopoietic function of bone marrow and infiltrate organs, and clinical manifestations similar to those of acute leukemia may appear. (C) Diagnosis and treatment Based on the patient’s medical history and clinical manifestations such as anemia, bleeding and infection, the doctor can easily make a preliminary judgment of “suspicion” by combining with routine peripheral blood tests, and further request the patient to undergo bone marrow aspiration examination, and take bone marrow specimens for cytology, cytochemical staining, chromosome culture and FISH testing, fusion gene, flow cytometry, and other tests. A number of tests such as fusion genes and immunophenotyping by flow cytometry will be performed to determine the diagnosis and further staging. Once the diagnosis and typing are clear, treatment can be started. For patients with acute leukemia, chemotherapy should be started as early as possible with adequate supportive therapy (alkalinization and hydration of urine; anti-infection; transfusion of red blood cells and platelets) to rapidly reduce the number of leukemia cells to less than 1 in 10,000 before chemotherapy and achieve complete remission (at the time of clinical diagnosis, the number of leukemia cells in the body of a patient with acute leukemia is about 1012, and by the time the patient achieves complete remission after chemotherapy, the number of leukemia cells in the body can be reduced to (the number of leukemia cells in the body of an acute leukemia patient at clinical diagnosis is reduced to 108, a reduction of about 10,000-fold). After reaching complete remission, the normal hematopoietic function of the bone marrow is restored, and the patient’s blood picture basically returns to normal, and the manifestations of anemia, infection, and bleeding are significantly reduced. This will be followed by consolidation therapy with the same or similar chemotherapy regimen, followed by an increase in drug dose or an intensive treatment with an optional non-cross-resistant chemotherapy regimen. Consolidation therapy for acute lymphoblastic leukemia is usually followed by the application of low-dose chemotherapeutic agents for about 2 years of maintenance therapy. To prevent and treat CNS leukemia, appropriate chemotherapeutic agents should also be selected for intrathecal lumbar puncture injection after complete remission. Theoretically, it is impossible to completely eliminate all leukemia cells by chemotherapy alone, because chemotherapy kills leukemia cells on a logarithmic scale, not to zero, and the survival of the remaining leukemia cells after several “baptisms” of chemotherapy indicates that these cells are highly resistant to chemotherapeutic drugs ( Once relapsed, leukemia cells are often resistant to multiple drugs, leaving no choice of treatment options. Therefore, chemotherapy alone is not sufficient for most types of acute leukemia patients to escape the fate of relapse. Therefore, the limitations of chemotherapy alone are obvious. In contrast, allogeneic bone marrow transplantation not only maximizes the killing of leukemia cells through mega-doses of chemotherapy or radiotherapy during the “pretreatment” process, but also further kills the remaining leukemia cells in the recipient’s body through a new healthy immune system rebuilt by the implanted donor’s hematopoietic stem cells (graft-versus-leukemia effect), resulting in Two-thirds of leukemia patients eligible for bone marrow transplantation are cured. However, the availability of bone marrow transplantation is influenced by the availability of a suitable donor, the patient’s age, physical condition, and financial situation, and there is a transplant-related mortality rate of about 30%. Acute promyelocytic leukemia is one of the few types of leukemia that can be cured by drugs alone. The specific drugs are all-trans retinoic acid (ATRA) and arsenious acid (ATO), which are used in combination with chemotherapeutic agents to cure the majority of patients with acute promyelocytic leukemia. With the continuous progress in molecular biology and molecular genetics research, various molecularly targeted therapies targeting the pathogenesis have also emerged. The most famous one is imatinib mesylate (Gleevec), a tyrosine kinase inhibitor that blocks the signaling action of the bcr/abl fusion gene product P210 fusion protein on chromosome Ph in chronic granulocytic leukemia cells, thereby inhibiting the proliferation of leukemia cells. With the advent of Gleevec, chronic granulocytic leukemia has become a chronic disease similar to hypertension and diabetes (for most patients) with lifelong medication. It is believed that more molecularly targeted drugs will be available in the near future to bring benefits to leukemia patients. (iv) Prevention Since the causative factors of leukemia are basically the same as those of MDS mentioned above, the preventive measures are also basically the same. Therefore, special attention should be paid to environmental, personal and dietary hygiene. Patients and their family members should wear masks and disinfect their hands, disinfect their living environment with ultraviolet light, clean their mouth and perianal area, and disinfect food. Patients and their families should wear masks and disinfect their hands, disinfect their living environment with UV light, clean their mouth and perianal area, and disinfect their food.