Crohn's disease (CD) is a chronic inflammatory bowel disease (IBD). In recent years, the incidence of CD in children has shown a significant upward trend globally, and it has also increased significantly in Chinese children. According to epidemiological studies, the incidence of CD in Chinese children is approximately 2.5 to 11 cases per 100,000 people per year. CD in children is usually more severe and can significantly affect the psychological and social functions as well as physical development of patients. Infliximab (IFX), as the first tumor necrosis factor-α (TNF-α) antagonist approved for the treatment of CD, specifically binds and neutralizes TNF-α, inhibiting intestinal inflammatory responses and promoting mucosal healing. In the field of pediatric CD, several studies have preliminarily confirmed that IFX monotherapy can effectively induce clinical remission, promote growth and development, and reduce hormone dependence. However, a considerable proportion (37.8% to 43.3%) of CD patients treated with anti-TNF-α therapy will develop secondary adaptive responses (LOR). Therefore, they need dose intensification, switching to other anti-TNF drugs, or switching to drugs with different mechanisms of action for intervention. Multiple studies have shown that the combination of anti-TNF-α drugs with immunomodulators may reduce the production of anti-drug antibodies and improve efficacy, thereby maintaining remission. The most commonly used immunomodulators for IBD are thiopurine drugs, such as azathioprine or 6-mercaptopurine. Some previous studies suggest that combination therapy may be superior to monotherapy in adult CD, but its efficacy and safety for this special group of children remain controversial: on the one hand, the immune system of children is not yet fully developed, and combined therapy may further increase the risks of infection and bone marrow suppression; on the other hand, children have urgent needs for growth and development, and the effectiveness and safety of combined therapy in improving growth retardation and promoting mucosal healing still require more high-quality evidence to support. Currently, there are limited clinical studies on the use of IFX monotherapy or IFX combined with azathioprine for pediatric CD in both domestic and international settings, and most of them are small-sample retrospective studies, lacking large-sample prospective randomized controlled trial (RCT) data. At the same time, there is also a lack of evidence on the optimal timing of combined therapy, dose adjustment strategies, and long-term follow-up safety (such as long-term tumor risk, fertility impact, etc.) for combined therapy, which cannot provide sufficient evidence for clinical decision-making. Based on the above background, this study aims to compare the efficacy and safety of IFX monotherapy and IFX combined with azathioprine in treating pediatric CD, in order to clarify the differences in efficacy of the two treatment regimens in inducing remission, maintaining remission, mucosal healing, and growth and development of pediatric CD, and to comprehensively analyze their short-term and long-term safety characteristics, in order to provide more reliable evidence-based medical evidence for individualized treatment of pediatric CD, optimize clinical treatment pathways, and ultimately improve the long-term prognosis and quality of life of children.
