The aim of this study was to compare the clinical features and outcomes of ulcerative colitis (UC) according to the age of onset in Korea.
A total of 1,141 patients who were diagnosed with UC between July 1987 and November 2013 at 11 tertiary hospitals were enrolled. The baseline disease characteristic and disease state at onset, treatment during the disease course were retrospectively reviewed among patients with young-onset (YO, < 20 years) and adult-onset (AO, ≥ 20 years). Severe outcome was defined as use of intravenous (IV) steroids, infliximab, immunosuppressant, or UC-related operation.
There were 55 YO patients (mean age, 17.8 ± 2.4) and 1,086 AO patients (mean age, 43.0 ± 13.6). High Mayo scores (7.7 ± 3.0 vs. 5.6 ± 2.7, 
UC with YO presented with more advanced clinical features at onset and more severe outcomes than the AO. YO cases require careful management and intense treatment strategies.