Crohn's Disease in Pediatric Patient

The goal of this clinical trial is to investigate whether there are significant differences in the efficacy of infliximab monotherapy and combined azathioprine therapy in treating pediatric Crohn's disease, as well as whether there are differences in the safety of these two treatment regimens during long-term use. The main questions it aims to answer are: Is infliximab combined with azathioprine superior to monotherapy in inducing and maintaining remission of Crohn's disease in children? In long-term treatment, can infliximab combined with azathioprine more effectively reduce disease activity and the occurrence of complications, but the incidence of adverse reactions is not higher than that of monotherapy? Researchers will compare the treatment of infliximab combined with azioprine with that of infliximab monotherapy to assess the efficacy and safety of both in inducing and maintaining remission of Crohn's disease in children. Participants will: Take drug ABC or a placebo every day for 4 months Experimental group: Infliximab, administered intravenously at 5mg/kg every 8 weeks at weeks 0, 2, 6 and thereafter, along with azathioprine, taken orally at 1.5-2.5mg/kg daily. Control group: Infliximab (Remicade), administered intravenously at 5mg/kg every 8 weeks at weeks 0, 2, 6 and thereafter. A comprehensive disease assessment will be conducted at the hospital in the 14th and 54th weeks. Record their symptoms, signs and test results.