PTGER4 and inflammatory bowel disease: Besides XIAP, polymorphisms in other genes modulating such biological functions as intestinal barrier integrity (HNF4A, PTGER4), adaptive immunity (IL12B, STAT4), and inflammasome regulation (MEFV) have all been implicated in susceptibility to various forms of IBD, suggesting that the driving forces for IBD are complex and unique to each patient [80,81,82,83,84,85].