Extraintestinal manifestations in Korean patients with inflammatory bowel disease: A nationwide population-based study from 2005 to 2017

BACKGROUND: Extraintestinal manifestations (EIMs) significantly contribute to morbidity in individuals with inflammatory bowel disease (IBD); however, population-based East Asian data remain limited. We evaluated EIM burden in a nationwide Korean IBD cohort. METHODS: This nationwide retrospective cohort study was conducted using data from the Korean National Health Insurance Service between 2005 and 2017. Individuals with ulcerative colitis (UC) or Crohn's disease (CD) were identified using the International Classification of Diseases-10th Edition and rare intractable disease codes. EIM incidence, associated risk factors, interval from IBD diagnosis to EIM onset, and trends by sex and age were examined. RESULTS: Among 69 414 individuals with IBD (48 689 UC, 20 725 CD), 42.23% developed at least 1 EIM. Dermatologic manifestations were the most common (17.02%), followed by musculoskeletal (16.36%), hepatopancreaticobiliary (15.48%), and ophthalmologic (7.83%) manifestations. Low socioeconomic status, smoking history, female sex, and higher Charlson Comorbidity Index scores independently correlated with EIM development in UC (hazard ratios of 2.14, 1.18, 1.15, and 1.08, respectively) and CD (hazard ratios of 1.98, 1.20, 1.18, and 1.09, respectively). Most EIMs developed within 4 to 6 years postdiagnosis, with musculoskeletal EIMs occurring earliest (median 42.9 months [interquartile range: 10.3-89.5 months]). Annual EIM incidence increased steadily over time across all age groups. CONCLUSIONS: EIMs affected 42.23% of Korean individuals with IBD, most frequently appearing 4 to 6 years postdiagnosis. Low socioeconomic status, smoking history, female sex, and higher Charlson Comorbidity Index scores consistently correlated with EIM occurrence, and incidence increased steadily over time, highlighting the need for sustained, personalized monitoring and timely intervention.