["Crohn's disease is a heterogeneous inflammatory bowel disease. The impact of age at diagnosis on the clinical course of patients varies widely as reported in the Western literature. Using the Vienna Classification, we seek to determine whether young Crohn's disease patients in an Asian population followed a different clinical course than old patients.", "The case records of 100 Crohn's disease patients who were treated at the Inflammatory Bowel Disease Center, Singapore General Hospital, were studied retrospectively. The age group and location of disease and behavior according to the Vienna classification were determined at diagnosis.", 'A1 group (age <40 years) defined as "young" and A2 group (age > or =40) defined as "old" contained 65 and 35 patients, respectively. Median age for the young group was 27.4 years and that for the old group was 52.6 years. Of the young patients, 66.7% flared at least once compared with 28.6% of the old patients, odds ratio of 5.0 (P < 0.001). Young patients were more likely to be steroid dependent (20.0% of A1 versus 8.6% of A2, P = 0.14), received azathioprine (38.5% of A1 versus 5.7% of A2, P < 0.001) and experienced complications (31% of A1 versus 20% of A2, P = 0.25)-numerically higher rates that did not reach statistical significance. There was no significant difference between the age groups for the location and behavior of disease as well as requirement for surgery.'] Does crohn 's disease run a more aggressive course in young Asian patients?