• Crohn's disease
• natural history
• outcomes
• surgery
• medical therapy
• gastrointestinal muscle
• IBD
• IBD models
• IBD clinical
• IBD basic research

In the last decade, we adopted the paradigm that most, if not all, patients with Crohn's disease are progressing towards a complicated stage of the disease. At St Antoine Hospital in Paris, France, the vast majority of patients initially had an inflammatory disease phenotype at diagnosis that progressed to penetrating or fibrostenotic disease over the course of 10–20 years.1 This seminal paper has been invoked countless times to make the case for top-down biological therapy in Crohn's disease. The profile of patients with a high risk of a debilitating disease course emerged from subsequent work by the same group and by other groups.2 ,3 Young patients, particularly those with perianal disease at onset are more likely to need surgery and several courses of steroids to control their disease. The phenotypic classification of Crohn's disease was amended accordingly, and this culminated in the now generally used Montreal criteria, which include perianal disease and age at disease onset.4

Data in a prospectively followed cohort from 1995 to 2009 (reported in this issue of GUT by the same group of investigators in Paris), seemingly deviate from their previous work.5 In this more recent cohort, almost half the patients were found to have a mild to moderate disease …