Growth impairment in Japanese children with inflammatory bowel disease: A multicenter prospective cohort study

To investigate the prevalence and characteristics of growth impairment (GI) in children with inflammatory bowel disease (IBD). In this prospective observational study, 402 children with ulcerative colitis (UC, n = 257) and Crohn's disease (CD, n = 145) were enrolled from the Japanese Pediatric IBD Registry (2012-2020). GI was defined by Paris classification criteria. Longitudinal outcomes were assessed in children with ≥2 years of follow-up (n = 307). At diagnosis, the GI prevalence was comparable between children with UC and CD (6.2% vs. 8.3%, p = 0.54). However, children with UC diagnosed at 0-4 years demonstrated significantly higher GI rates (35.3%) than older children (p < 0.001). All children with CD experiencing GI had small intestinal lesions. Among those with GI at diagnosis, fewer children with UC (9%) recovered growth at a 2-year follow-up than those with CD (50%). Among children with normal growth at baseline, new-onset GI occurred in 23% of UC and 16% of CD cases. Of these, 31% recovered within 2 years, while persistent GI was observed in 16% of UC and 11% of CD cases. Prolonged corticosteroid use at 1 year was more frequent in UC (31% vs. 19%, p = 0.02) and was significantly associated with persistent GI. Distinct growth patterns exist in Japanese children with IBD. Children with UC diagnosed at 0-4 years are particularly vulnerable and may benefit from early, steroid-sparing treatment. The association between small intestinal lesions and GI in CD emphasizes the importance of small bowel evaluation. Age-specific, patient-centered growth monitoring is crucial to optimize long-term outcomes.