Crohn's disease is most often found in a section of the small intestine called the ileum, but Crohn's can happen anywhere in your GI tract from the mouth to the anus.n addition to Crohn's, other autoimmune disorders include rheumatoid arthritis, ulcerative colitis, psoriasis, psoriatic arthritis, ankylosing spondylitis, lupus, and Graves' disease. Inflammatory bowel disease, or IBD, is a category of bowel disorders that includes both ulcerative colitis and Crohn's disease.