 The results would provide a better knowledge of the etiopathogenic ways in CD and would downstream open the way towards clinical trials focused on specific microbiota disorders according to age at CD onset. This project will help to decipher the potential involvement of specific bacteria in the physiopathology of CD. This could lead to the development of new therapeutic strategies either using optimized current treatments targeting bacteria. Data from clinical trials which for the great majority rarely include paediatric patients and set an upper limit for study eligibility at 65 years of age are thus focusing on adult-onset disease. Thus the potential specificities of paediatric- and elderly-onset diseases are not taken into account. A better knowledge of characteristics of CD at the extreme of life will be important to set up innovative clinical trials including specific therapeutics adapted to patients where disease occurred at the extreme age of life, especially as these patients did not benefited of specific trials. The ultimate goal is a better quality of care delivered to paediatric- and elderly-onset CD patients. 