Ileitis's an inflammation of the ileum, a portion of the small intestine. Crohn's ileitis's a type of Crohn's disease affecting the ileum. Terminal ileitis: Crohn's disease, a chronic inflammatory disease of the intestine involving only the end of the small intestine (the terminal ileum). Crohn's disease affects primarily the small and large intestines, but can occur anywhere in the digestive system between the mouth and the anus. The disease's named after Burrill Crohn who described the diseas… (More on Ileitis)