Total number of genome regions known to be associated with inflammatory bowel disease is up to 99.
IBD pathogenesis involves multiple environmental factors[smoking, altered intestinal flora, antibiotics, food allergy and other less clearly understoon ones like hygiene, breast feeding, high sugar intake etc] acting on a genetically susceptible host. The term "genetically susceptible" involves a large number of phenotypic [like altered ntestinal permeability and colonic mucus] and immunitypic alterations involving the vast array of cytokines, chemokines, growth factors, interleukines, cell adhesion molecules which are responsible for keeping the gut in its "normal state of controlled inflammation" by acting in permutatons and combinations. No wonder alteration in any of the large number of genes which control the production of these molecules can disturb this "normal state of controlled inflammation"
the literature "Advances in IBD genetics" has suggested that there are more than 160 loci containing IBD susceptibility genes