Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD), which typically affects only the mucosa of the colon in a continuous fashion, starting in the rectum and advancing proximally to varying degrees. This is in contrast to Crohn disease, another form of IBD which can cause inflammation anywhere along the gastrointestinal tract from the oral cavity to the anus, often in a patchy distribution. The proposed role of genetics in IBD has long been an observation of investigators noting strong heritability patterns within families. UC has a varied presentation, likely dependent upon the degree and extent of inflammation present in the colon. Many of the genes implicated in UC control immune functions such as autophagy, microbial recognition, and regulation of both the adaptive and innate immune systems. Classic macroscopic findings of UC include friable, edematous, granular and ulcerated mucosa starting at the anal verge and progressing proximally.