Acute lymphocytic leukemia is a life-threatening disease that normally develops as a malignant transformation of lymphocyte precursor cells and rapidly replaces normal cells in the bone marrow. Acute lymphoblastic leukemia can occur at any age, but is most common in children, accounting for 25% of all malignancies in children under the age of 15. It occurs mostly in children between the ages of 2 and 5 years. It can also involve adolescents, and in adults it is common in people over 65 years of age. When a person develops lymphocytic leukemia, very early immature leukemia cells accumulate in the bone marrow, destroying and replacing normal hematopoietic cells. They can be released into the blood and reach the liver, spleen and lymph nodes, and even brain tissue. They can invade the cerebrospinal membrane causing meningeal leukemia, as well as causing anemia, liver and spleen and other organ damage. Clinical manifestations and diagnosis The initial symptoms are usually due to the inability of the bone marrow to produce enough normal cells. Fever and excessive sweating often suggest infection. Progressive weakness, fatigue and pallor suggest anemia and erythrocytopenia. Thrombocytopenia often causes nosebleeds, bleeding gums, skin purpura, and bleeding after brushing teeth. Leukemic cell infiltration in the skull can cause headache, vomiting, and irritability, while leukemic cells in the bone marrow can cause bone and joint pain. When the liver and spleen are enlarged due to leukemia cells, the patient may experience a feeling of fullness and sometimes abdominal pain. Blood tests such as a complete blood count provide the first evidence that the patient has acute lymphoblastic leukemia. The total white blood cell count may be decreased, normal or increased, but the red blood cell and platelet counts are almost always decreased. More importantly, immature cells (primitive cells) may be seen in the blood specimen under the microscope. Since primitive cells are not present in normal blood, their presence is required for the diagnosis of leukemia. However, bone marrow is punctured and biopsied to confirm the diagnosis and to determine the leukemia typing. Treatment and prognosis Until effective treatment for leukemia becomes available, most patients with acute lymphoid leukemia die within 4 months of diagnosis. Currently, almost about 80% of children and about 30% to 40% of adults with acute lymphoblastic leukemia have been cured. About 90% or more of patients with acute lymphoblastic leukemia (mostly children) are given one course of chemotherapy to achieve control (complete remission). Many patients relapse, but 50% of pediatric cases show no signs of leukemia relapse after 5 years of treatment. children between the ages of 3 and 7 years have the best prognosis; patients under 2 years of age and older patients have the worst prognosis. The prognosis of leukemia can be influenced by the number of leukocytes at the time of initial diagnosis, especially by the abnormal chromosomal status. Chemotherapy has a very high efficacy and it is usually administered in phases. The goal of the initial treatment is to destroy the leukemic cells so that normal hematopoietic cells can regrow in the bone marrow to achieve remission. At this point, patients receiving chemotherapy will be hospitalized for several weeks, depending on how quickly the bone marrow recovers. Patients may require blood transfusions to correct anemia, platelet transfusions to stop bleeding, and antibiotics to combat infection until normal bone marrow function is restored. Intravenous rehydration and oral purinergics help remove harmful substances from the body, such as uric acid released during leukemic cell destruction. Treatment is often a combination of several drugs, with each dose being given repeatedly over several days or weeks. Combination chemotherapy regimens include glucocorticoids, weekly vincristine, and intravenous anthracyclines (often erythromycin) or menadione, sometimes with cyclophosphamide, while other drugs should be given as prescribed by the doctor. Treatment of intracranial meningeal leukemia is commonly done with methotrexate and/or cytarabine injected directly into the cerebrospinal fluid and may be combined with cranial radiotherapy. Because leukemic cells readily disseminate to the central nervous system, prophylactic cranial chemotherapy is often given even in the absence of clear evidence of intracranial tumor dissemination. A few weeks after the completion of the initial intensive chemotherapy aimed at destroying the leukemic cells, re-chemotherapy (consolidation therapy) should be started to salme any remaining leukemic cells. More chemotherapy drugs (repeating previously used drugs) or new chemotherapy drugs are used in combination. Further treatment (maintenance chemotherapy) often consists of tree drugs, or maintenance therapy using lower doses typically takes 2 to 3 years. For those high-risk patients with specific chromosomal alterations, bone marrow transplantation should be done after the initial remission. As can be seen, testing for chromosomes, fusion genes, and immunophenotype at the time of initial diagnosis is very important. Leukemia cells can reappear after treatment remission (called relapse), often in the bone marrow, testes, and brain. Leukemia relapse is most problematic in the bone marrow. Chemotherapy needs to be restarted, and although most patients respond to chemotherapy, the risk of relapse is high, especially in adults and children under 2 years of age. Intracranial leukemia relapse is usually treated with chemotherapy drugs as intralesional injections two to three times a week, and testicular leukemia requires chemotherapy or local radiotherapy. For relapsed patients hematopoietic stem cell transplantation is the best option. The current options for HSCT are sibling compatible donor, HLA compatible unrelated donor, HLA incompatible related or unrelated donor and cord blood. Patients who relapse and then cannot undergo stem cell transplantation often respond and are poorly tolerated to more chemotherapeutic agents, but still have the potential for remission. End-stage patients who have failed to respond to treatment should be treated with enhanced hospice care.