Definition of phenotypic characteristics of childhood-onset inflammatory bowel disease

Background & Aims: Childhood-onset inflammatory bowel disease (IBD) might be etiologically different from adult-onset IBD. We analyzed disease phenotypes and progression of childhood-onset disease and compared them with characteristics of adult-onset disease in patients in Scotland. Methods: Anatomic locations and behaviors were assessed in 416 patients with childhood-onset (276 Crohn's disease [CD], 99 ulcerative colitis [UC], 41 IBD type unclassified [IBDU] diagnosed before seventeenth birthday) and 1297 patients with adult-onset (596 CD, 701 UC) IBD using the Montreal classification. Results: At the time of diagnosis in children, CD involved small bowel and colon (L3) in 51% (138/273), colon (L2) in 36%, and ileum (M) in 6%; the upper gastrointestinal (GI) tract (L4) was also affected in 51%. In 39%, the anatomic extent increased within 2 years. Behavioral characteristics progressed; 24% of children developed stricturing or penetrating complications within 4 years (vs 9% at diagnosis; P < .0001; odds ratio [OR], 3.32; 95% confidence interval [CI], 1.86 - 5.92). Compared with adults, childhood-onset disease was characterized by a "panenteric" phenotype (ileocolonic plus upper GI [L3 + L4]; 43% vs 3%; P