My daughter was diagnosed with Crohn's at age 9. While it tends to hit more often in later adolescence, there are cases of very young children being diagnosed ( know a woman whose daughter was an infant when diagnosed). There are varying symptoms, I've known some people that had constipation instead of diarrhea. It can't hurt to ask for a referral to a GI, especially if you have any type of inflammatory bowel disease in your family history. Usually the diagnostic tests are a colonoscopy and/or an Upper GI, but obviously you don't want to put a very young child through either of those unless you absolutely have to. There are all kinds of things that can cause stomach issues/abdominal pain; it's just that the weight loss struck me because I remember it all too well!
Unfortunately I know way too much about this disease. www.ccfa.org is the site for the national organization in the U.S., FYI.
