New developments in aetiological mechanisms of inflammatory bowel disease.

This review in depth considers the new knowledge and some hypotheses accumulated during the last few years regarding the aetiology of inflammatory bowel disease. The role of genetic susceptibility, in particular the first gene where a mutation is responsible for part of patients with Crohn's disease, is discussed. The consequence for phenotype variability and the environmental influences regarding manifestation of the disease are analysed by experts. Finally, alternative hypotheses including an immune deficiency and defective local bacterial response are demonstrated.