I. Standard hospitalization process of APL clinical pathway for primary care children (a) The standard hospitalization days are within 40 days. (B) Entry pathway criteria. 1. The first diagnosis must be consistent with the Acute Promyelocytic Leukemia (APL) disease code for children (ICD-10: C92.401, M9866/3). 2. When the patient also has other disease diagnoses but does not require special treatment during hospitalization and does not interfere with the implementation of the clinical pathway process for the first diagnosis, he or she may enter the pathway. (c) Clear diagnosis and routine examination for admission takes 3-5 days (referring to working days). 1.Required examination items: (1) routine blood, routine urine, routine stool; (2) liver and kidney function, electrolytes, coagulation function, blood type, pre-transfusion examination; (3) chest X-ray plain film, electrocardiogram, abdominal ultrasound, fundus examination. (2) For fever or suspected infection: pathogenic microbial culture, imaging; (3) Bone marrow examination (morphology including histochemistry), immunophenotyping, cytogenetics, leukemia-related gene (PML/RARa and its variants) detection. 4. The patient and family members sign the following consent forms: notification of serious or critical illness, consent form for bone puncture, consent form for lumbar puncture and intrathecal injection, informed consent form for chemotherapy, informed consent form for blood transfusion, and consent form for intravenous cannulation (when available). (D) Pre-chemotherapy preparation. 1.Patients with fever are recommended to have immediate pathogenic microbial culture and use antimicrobial drugs. Cephalosporins (or penicillins) can be used for anti-inflammatory treatment, and those whose fever does not remit after 3 days can be considered for replacement of carbapenems and/or glycopeptides and/or antifungal treatment; patients with clear organ infections should choose appropriate antimicrobial drugs according to the site of infection and pathogenic microbial culture results. 2. For patients with Hb80g/L, PLT30×109/L or active bleeding, transfusion of concentrated red blood cells, single or multi-collected platelets should be given respectively. Those with cardiac insufficiency can relax the transfusion indications. 3. With coagulation abnormalities, transfuse relevant blood products. Fibrinogen 1.5g/L, transfusion of fresh plasma or concentrated fibrinogen. (E) Chemotherapy starts on the 1st day of diagnosis. (vi) Chemotherapy regimen. One of the following regimens can be used for induction therapy 1.ATRA: ATRA 20-30mg・m-2・d-1×28-40d. 2.ATRA+DNR: ATRA 20-30mg・m-2・d-1×28-40d, DNR starts on the 4th day after ATRA treatment, the maximum amount can be 135mg・m-2, split into at least 3 days of administration. 3. ATRA+ATO: ATRA 25-45mg・m-2・d-1×28-40d, ATO 0.2mg・Kg-1・d-1×28-35d, and cytotoxic drugs such as DNR and hydroxyurea can be added in appropriate amounts according to the changes in the number of white blood cells during treatment. (vii) The examination items that must be rechecked within 30 days after treatment. 1.Blood routine, liver and kidney function, electrolytes, coagulation function. 2.Organ function assessment. 3.Bone marrow examination (if the hematological response is not adequate at 30 days, it can be extended until the discharge date). 4.Micro residual lesion detection (when available). (H) Treatment during and after chemotherapy. 1, infection prevention and control: febrile patients are recommended to immediately perform pathogenic microbial culture and use antibacterial drugs, cephalosporins (or penicillins) can be used for anti-inflammatory treatment; those whose fever does not resolve after 3 days can be considered to replace carbapenems and/or glycopeptides and/or antifungal drugs for treatment; patients with clear organ infection should choose the appropriate antibacterial drugs according to the site of infection and pathogenic microbial culture results. 2.Prevent and control organ function damage: antiemetic, hepatoprotective, hydration, alkalinization, prevention and control of uric acid nephropathy (allopurinol), treatment of induced differentiation syndrome (dexamethasone), acid suppressant, etc. 3.Component transfusion: For patients with Hb80g/L, PLT30×109/L or active bleeding, transfusion of concentrated red blood cells, single or multi-collected platelets respectively, if there is a tendency of DIC, then PLT50×109/L should be transfused with platelets and DIC treatment drugs such as heparin. If there is cardiac insufficiency, the indication for transfusion can be relaxed. 4. Hematopoietic growth factor: absolute neutrophil value (ANC) ≤ 1.0×109/L after chemotherapy, granulocyte colony-stimulating factor (G-CSF) 5μg・Kg-1・d-1 can be used. (ix) Discharge criteria. 1.Generally good condition. 2, No complications and/or comorbidities requiring hospitalization. (X) Variation and cause analysis. 1, Those with infection, anemia, bleeding and other comorbidities before, during and after treatment need relevant diagnosis and treatment, which may prolong hospitalization and lead to increased costs. 2, Those who do not achieve complete remission after 40 days of induction differentiation therapy withdraw from the pathway. 3.If the cerebrospinal fluid examination after lumbar puncture shows the presence of CNSL, withdraw from this pathway and enter the related pathway.