Inflammatory bowel diseases are a complex and diverse group of disorders. Whereas the disease in the majority of patients are caused by a polygenic contribution, in a small fraction of patients a single gene can cause intestinal inflammation. A systematic analysis of the group of monogenic diseases suggests a diverse role of epithelial cells maintaining the epithelial barrier function but also defects in antimicrobial activity of phagocytes, hyperinflammatory defects, defective immune regulation. We will discuss a taxonomy of inflammatory disease and how rare genetic defects can inform on subgroups of classical polygenic disease.
