Clinical characteristics and prognosis of infant onset inflammatory bowel disease in Chinese children: a 10-year single-center experience.

BACKGROUND: Infant-onset inflammatory bowel disease (IO-IBD) is a rare, severe subtype of pediatric IBD with insufficient clinical and genetic data in northern China. This study aimed to investigate the clinical characteristics, gene mutation spectrum, treatment responses and long-term prognosis of IO-IBD in children in northern China, and to provide evidence-based basis for the standardized diagnosis and treatment of this disease. METHODS: A retrospective analysis was conducted on the clinical data of 98 children diagnosed with IO-IBD in Beijing Children's Hospital from January 2016 to December 2025. According to clinical phenotypes, the patients were divided into Crohn's disease (CD) phenotype and ulcerative colitis (UC) phenotype. The clinical features, laboratory examinations, treatment regimens and prognoses were compared between the two groups. Whole-exome sequencing or IBD gene panel testing was performed on 77 children to analyze the differences in clinical characteristics and prognoses between monogenic and non-monogenic IO-IBD. RESULTS: Among the 98 children with IO-IBD, 64 (65.3%) had CD phenotype and 34 (34.7%) had UC phenotype. The median age of onset in the entire cohort was 4 months. There was no significant difference in the median age of onset between CD and UC phenotype children (5.0 vs. 4.0 months, P=0.16), but the incidence rates of perianal lesions and penetrating disease behavior were significantly higher in the CD group. Among the 77 children who underwent genetic testing, 39 (50.6%) were identified with definite monogenic mutations, of which IL-10RA gene mutations accounted for 84.6% (33/39). Children with monogenic IO-IBD had more severe disease conditions. The median Pediatric Crohn's Disease Activity Index (PCDAI) score in CD phenotype (60, 49.0-67.5 vs. 32.5, 22.5-42.5; P<0.01), median Pediatric Ulcerative Colitis Activity Index (PUCAI) score in UC phenotype (47.5, 35.0-65.0 vs. 35, 25.0-45.0; P=0.02) and mortality rate (28.21%, 14.7-45.3% vs. 1.72%, 0.04-9.2%; P<0.01) were significantly higher than those in non-monogenic children. Among the 33 children with IL-10RA gene mutations, 6 successfully underwent allogeneic hematopoietic stem cell transplantation (HSCT), with an overall survival rate of 100% (54.1-100%). For the remaining 27 patients who did not receive HSCT, 14 died during follow-up, corresponding to a mortality rate of 51.9% (32.0-71.3%). CONCLUSIONS: IO-IBD in children in northern China is predominantly CD phenotype with a high proportion of monogenic causes, among which IL-10RA mutations are dominant. Children with IL-10RA mutations have more severe disease and higher mortality rates, and early HSCT can significantly improve their prognosis. It is recommended that all children with IO-IBD should routinely undergo IL-10RA gene testing, and HSCT indications should be evaluated as early as possible after diagnosis.