To establish a population pharmacokinetic and pharmacodynamic model of rituximab in children with hemopathy. To optimize the administration of rituximab in the treatment of children based on pharmacokinetic model.

hemotherapy for children with lymphoma: rituximab (375mg/m2 BSA) was added intravenously from COPADM1 regimen. once every 3 weeks to 4 weeks, combined with corresponding chemotherapy, a total of 4 times.

Rituximab (375mg/m2 BSA) was administered intravenously for lymphoproliferative diseases and Epstein-Barr(EB) virus-associated B lymphoproliferative diseases after hematopoietic stem cell transplantation. Once a week, a total of 4 times.

Primary immunologic thrombocytopenic purpura(ITP) and autoimmune hemolytic anemia(AIAH) patients received rituximab (100mg/m2 BSA) intravenously once a week, a total of 4 times.

The children were divided into group A and group B according to the disease type, and each group was randomly divided into two groups (group 1 and group 2) and assigned blood collection points.

Burkitt's lymphoma diffuse large B-cell lymphoma follicular lymphoma and other mature B-lymphomas were in group A. Hematopoietic stem cell transplantation, EPstein-Barr virus associated lymphocyte proliferative disease, lymphocyte proliferative change, primary immunologic thrombocytopenic purpura(ITP) and autoimmune hemolytic anemia(AIAH) were in group B.

Group 1: Children in the first group were collected 0, 12, 24, and 72 h after the first dose, 0h before and after the second dose, 0h before and after the third dose, 0h before and after the last dose, 48, and 96 h after the last dose. Venous blood was collected at 12 time points.

Group 2: Children in the second group were collected 0, 12, 48, and 96 h after the first dose, 0h before and after the second dose, 0h before and after the third dose, 0h before and after the last dose, 24, and 72 h after the last dose. Venous blood was collected at 12 time points.

Inclusion Criteria:

• Children aged 6 months to 18 years (including 6 months and 18 years), male or female.
• Burkitt's lymphoma, diffuse large B-cell lymphoma, follicular lymphoma and other mature B-cell lymphoma confirmed by histology or cytology, hematopoietic stem cell transplantation, EB virus associated B-cell proliferative diseases, b-cell proliferative changes, immune thrombocytopenia, Autoimmune hemolytic anemia and other patients with rituximab indications should be treated with rituximab monotherapy or combination.
• Eastern Cooperative Oncology Group(ECOG) physical status score was 0-2.
• Life expectancy was at least six months.
• Women and men with reproductive potential must agree to use effective contraceptive methods during and after treatment.
• The subjects or their parents or guardians fully know and sign the informed consent, and the subjects can cooperate to complete the follow-up.

Exclusion Criteria:

• Patients with known hypersensitivity to rituximab and rat protein.
• Previously known active infection of human immunodeficiency virus (HIV), hepatitis B virus (HBV) or hepatitis C virus (HCV), except for the following patients: Hepatitis B infection [hepatitis B surface antigen (HbsAg) or hepatitis B core antibody (HbcAb) positive] but negative results of HBV DNA polymerase chain reaction (PCR) can be included in the group.
• A confirmed history of progressive multifocal leukoencephalopathy (PML).
• Exclusion criteria associated with rituximab: tumor cell CD20 negative.
• Received live vaccine within 4 weeks prior to enrollment.
• Received immunoglobulin therapy within 3 months prior to enrollment.
• Participants in the clinical trials of other drugs and taking the test drugs within 3 months.
• Any other medical condition, metabolic abnormality, physical abnormality, or laboratory abnormality of clinical significance that, in the investigator's judgment, has reason to suspect that the patient has a medical condition or condition unsuitable for rituximab or that would affect the interpretation of study results or place the patient at high risk.

Age 6 months to 18 years, histologically or cytologically proven mature B lymphoma such as Burkitt's lymphoma, diffuse large B cell lymphoma, follicular lymphoma, hematopoietic stem cell transplantation, and Epstein-Barr virus associated B lymphoproliferative disease, B cell lymphoproliferative alteration, immune thrombocytopenia. Children with autoimmune hemolytic anemia and other diseases that meet the indication of rituximab and need rituximab monotherapy or combination therapy.