Both me and my sister have both of these diseases. I have had Type 1 Diabetes since the age of 4, now going on 18 years and my sister was not diagnosed with chrons until she was 12 years of age but it took them years to figure out what was wrong with her.
The funny thing about both of us having auto-immune disorders is the fact that we are the only 2 people in family history to be diagnosed. No one else has had any related issues or been diagnosed, not even are mom and dad.
I have found that over the last couple of years that my sister has had a much harder time with her disease than I have with mine. But I believe that the Lord has blessed both of our lives.
I currently work as a clinical technician/nurse extern at our local childrens hospital on the Endocrinology/CF floor where we get alot of the chronic disoreders and I am able to help them cope with what to expect with both disorders.
This is the response from the Crohn's and Colitis Foundation of America on whether there is a connection between Crohn's Disease and Type 1 Diabetes:
We don't know of any research that has indicated a connection between diabetes and Crohn's. However, although Crohn's disease is generally considered by many to be an auto-immune disease (although since the mechanisms are not yet completely understood, it has not "officially" been classified as such) and a connection between autoimmune diseases has been noted. For a very interesting examination of this, you may want to look at the article, "Autoimmunity - The Common Thread," on the American Autoimmune Related Diseases Association, Inc.'s web site at: http://www.aarda.org/common_thread_art.html
Both diseases are thought to be caused by an autoimmune system malfunction. Although this is just a theory in the study of Crohn's Disease, it would tend to indicate that a child whose autoimmune system attacks his or her pancreas cells may also be a candidate for the autoimmune system causing problems elsewhere.
Also, some researchers in Crohn's Disease treatments tend to believe that bacterial overgrowth can be the cause of some of the inflammation. We do know that a diabetic person whose sugar levels are frequently high can be more susceptible to bacterial infection than healthy people because high blood sugars make the body a perfect breeding ground for bacteria. Check this web site for more information about bacteria and Crohn's Disease: http://www.crohns-disease-treatments.com/html/antibiotics.php3
So those two facts would cause me to be aware of possible connections between the two diseases if my child was complaining of frequent stomach-aches and had some of the other symptoms. Check out this web site for more information on Crohn's Disease and its symptoms: http://digestive.niddk.nih.gov/ddiseases/pubs/crohns/index.htm
Also, if your child does complain of stomach-aches, I would certainly have him or her checked for Celiac Disease (an inability to digest gluten), for there does seem to be a frequent link to Celiac Disease and Type 1 diabetes. Celiac Disease can actually be symptom-free for years, and there are doctors who suggest that every diabetic be checked for it since there are proven statistics that seem to indicate that diabetics are frequently also victims of this disorder.
However, if your child is not complaining of pain and seems comfortable, I would not think you automatically need to check for Crohn's just because of the diabetes. With Crohn's Disease, there definately ARE symptoms when it is present.
I am not a physician and thus cannot answer your question about statistics of folks who have both diseases. I have fired off an e-mail to a Crohn's Disease organization in hopes of getting a firm answer to your question as far as real statistics are concerned. So stay tuned for more information.