Phenotypic characteristics of pediatric inflammatory bowel disease in Japan: results from a multicenter registry

Background/Aims: There are few published registry studies from Asia on pediatric inflammatory bowel disease (IBD). Registry network data enable comparisons among ethnic groups. This study examined the characteristics of IBD in Japanese children and compared them with those in European children. Methods: This was a cross-sectional multicenter registry study of newly diagnosed Japanese pediatric IBD patients. The Paris classification was used to categorize IBD features, and results were compared with published EUROKIDS data. Results: A total of 265 pediatric IBD patients were initially registered, with 22 later excluded for having incomplete demographic data. For the analysis, 91 Crohn’s disease (CD), 146 ulcerative colitis (UC), and 6 IBD-unclassified cases were eligible. For age at diagnosis, 20.9% of CD, 21.9% of UC, and 83.3% of IBD-unclassified cases were diagnosed before age 10 years. For CD location, 18.7%, 13.2%, 64.8%, 47.3%, and 20.9% were classified as involving L1 (ileocecum), L2 (colon), L3 (ileocolon), L4a (esophagus/stomach/duodenum), and L4b (jejunum/proximal ileum), respectively. For UC extent, 76% were classified as E4 (pancolitis). For CD behavior, B1 (non-stricturing/non-penetrating), B2 (stricturing), B3 (penetrating), and B2B3 were seen in 83.5%, 11.0%, 3.3%, and 2.2%, respectively. A comparison between Japanese and European children showed less L2 involvement (13.2% vs. 27.3%, P <0.01) but more L4a (47.3% vs. 29.6%, P <0.01) and L3 (64.8% vs. 52.7%, P <0.05) involvement in Japanese CD children. Pediatric perianal CD was more prevalent in Japanese children (34.1% vs. 9.7%, P <0.01). Conclusions: Upper gastrointestinal and perianal CD lesions are more common in Japanese children than in European children.