Pediatric modification of the Montreal classification for inflammatory bowel disease: The Paris classification

Background: Crohn's disease and ulcerative colitis are complex disorders with some shared and many unique predisposing genes. Accurate phenotype classification is essential in determining the utility of genotype–phenotype correlation. The Montreal Classification of IBD has several weaknesses with respect to classification of children. The dynamic features of pediatric disease phenotype (change in disease location and behavior over time, growth failure) are not sufficiently captured by the current Montreal Classification. Methods: Focusing on facilitating research in pediatric inflammatory bowel disease (IBD), and creating uniform standards for defining IBD phenotypes, an international group of pediatric IBD experts met in Paris, France to develop evidence‐based consensus recommendations for a pediatric modification of the Montreal criteria. Results: Important modifications developed include classifying age at diagnosis as A1a (0 to