Genetic & Environmental Factors: Crohn’s Disease & Celiac Disease

Dr. Hugh Freeman, a gastroenterologist at University of British Columbia Hospital has authored a number of papers over the past several years documenting his findings on the development of Inflammatory Bowel Diseases (IBD), and most recently, adult celiac disease in members of the immigrant population, most notably the Indo-Canadian community in British Columbia.

In findings reported in 2001¹, Dr. Freeman furthered the study of familial forms of Crohn’s disease with his study of an Indo-Canadian family consisting of three siblings with Crohn’s disease first diagnosed between the ages of 15 and 27 years, which was 6 to 11 years after their arrival in Canada. Subsequently, their father was diagnosed with the disease at the age of 76, after almost three decades in Canada. The family emigrated from Uganda.

These results support findings of several other recent studies that, “genetic or inherited factors appear to be critical in the pathogenesis of Crohn’s disease.” A proband with newly diagnosed Crohn’s disease has about a 10-fold or greater likelihood of having a positive family history of Crohn’s disease. If there is a relative, particularly a sibling, with Crohn’s disease, the risk of developing Crohn’s disease has been described to be as much as 30-fold.” The study further indicates a high degree of concordance in the three siblings for a number of clinical features, such as the site and type of behaviour of the disease. The difference noted in the clinical features of the father and the lateness of his presenting with symptoms also supports other studies that there may be generational differences in the time re-quired before a diagnosis can be established in the older generations.

In this family, the disease was diagnosed only after prolonged residence in Canada, supporting the view that Crohn’s disease arises in individuals with a genetic predisposition following exposure to some, as yet unknown, common environmental factor.

In several previous studies of Indo-Canadian individuals with IBD completed in 1998² and 2000³, similar results support the theory of genetic predisposition followed by exposure to common, as yet unknown, environmental factors encountered during residence in North America for periods averaging 8.9 years for the development of Crohn’s disease and 13.5 years for ulcerative colitis.

After another recent study, Dr. Freeman reports that celiac disease, another gastrointestinal disease thought to be a genetically based disorder mainly from European countries and those countries, including North America, to which Europeans have emigrated, has now been shown to occur in Asian populations living in North America.⁴

This latest study documents an experience with biopsy-defined celiac disease in Asian immigrants as well as those of Asian descent born in Canada, from differing ethnic backgrounds. The study included 14 Asians diagnosed in 1988 in a single Canadian teaching hospital. Of the 14 patients, 11 were Indo-Canadians. The findings suggest that this occurs far more frequently than is currently appreciated, particularly in those of Punjabi descent. Once again, the results indicate a genetic predisposition [largely but not solely], followed by exposure to common environmental factors [such as, wheat].

Note: A proband is a person forming the starting point for the genetic study of a family.

Claudia Roberts, MBA, CGA,
First published in The Inside Tract® Newsletter Issue 140 November/December 2003

References:

1. Freeman, Dr. Hugh J. and Hershfield, Dr. Noel B., “Anticipation in an Indo-Canadian family with Crohn’s disease”, Canadian Journal of Gastroenterology Vol 15 No 10 October 2001
2. Freeman, Dr. Hugh J., “Inflammatory bowel disease with cytoplasmic-staining antineutrophil cytoplasmic antibody and extensive colitis”, Canadian Journal of Gastroenterology Vol 12 No 4 May/June 1998
3. Freeman, Dr. Hugh J., “Inflammatory bowel diseases in Indo-Canadians with and without antineutrophil cytoplasmic antibodies”, Canadian Journal of Gastroenterology Vol 14 No 1 January 2000
4. Freeman, Dr. Hugh J., “Biopsy-defined adult celiac disease in Asian Canadians”, Canadian Journal of Gastroenterology Vol 17 No 7 July 2003