[Pathophysiology of inflammatory bowel disease].

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory bowel diseases (IBDs) of unknown origin. Current data suggest that the interaction of genetic, immunologic and environmental factors leads to chronic inflammation. In UC, the inflammation is limited to the mucosa whereas in CD, the whole bowel wall may be affected. The concept of genetic background is supported by the increased prevalence of CD within certain populations and individual families and by the results of twin studies. It is believed that not only the phenotype (CD or UC), but also the clinical course are influenced by genetic factors. It is unknown which trigger induces chronic immune stimulation. It could be either a nutritional antigen, a self antigen, a component of the normal gut flora or certain bacteria such a mycobacteria. The chronic immune stimulation may be due to a dysbalance of pro-inflammatory and inhibitory cytokines. Besides cytokines, a variety of different inflammatory mediators have a crucial role for the inflammatory process. Smoking has a significant effect on occurrence and outcome of CD and UC.