Abstract
Genetic anticipation, associated elsewhere with monogenic neurological disorders, has been hypothesized to be present in familial forms of Crohn's disease. Usually, with studies of parent-child pairs, the parent who is initially diagnosed is older at the onset of disease than the child. With each successive generation, an apparent increase in disease severity or behaviour occurs. This phenomenon is believed to have a molecular basis. In the present report, an Indo-Canadian family with Crohn's disease is described. In all members of the family, 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. Three siblings with Crohn's disease, first diagnosed between ages 15 and 27 years, or six to 11 years after arrival in Canada, had phenotypically concordant disease localized in the ileum and colon, with fistulizing complications, including perianal sepsis. Crohn's disease was only diagnosed in the father at the age of 76 years, almost three decades after his arrival in Canada. His disease was localized to the ileum and had a fibrostenosing behaviour. This is the first reported instance of familial Crohn's disease in an immigrant population, illustrating potential biases in genetically based studies of Crohn's disease that rely solely on phenotypic expression.