Crohn's disease however can increase your risk of colon cancer but only if you have significant colonic involvement. If only the small intersine, such as the ileum, is involved with inflammation, then your colon cancer risk would be considered average and screening starts at age 50. For significant Crohn's colitis inflammation, then more frequent screening by colonoscopy may be needed as the risk for colon cancer is related to the underlying inflammation and not to sporadic polyps.
Hope that helps.
If your Crohn's disease involves your colon, you are also at increased risk for colon cancer based on the Crohn's disease. Careful follow up with your gastroenterologist is essential both to manage your Crohn's but also for cancer risk stratification and appropriate screening.
(M. Jonathan Bern MD)