Concordance regarding disease type and phenotypic characteristics among patients with familial inflammatory bowel disease.

Background and Aims The phenotypic concordance among familial cases of inflammatory bowel disease (IBD) has been rarely reported. Thus, the present study aimed to evaluate the concordance regarding disease type and phenotypic features in a large cohort of Korean patients with IBD. Methods A total of 6647 patients with IBD who visited the Asan Medical Center between June 1989 and September 2016 were enrolled in the study. When at least two familial cases existed in our cohort, they were included in the concordance analysis (kappa index). The concordance between younger and older members for IBD type [Crohn's disease (CD) and ulcerative colitis (UC)] and phenotypic characteristics such as disease extent and location, disease behavior, the use of medication, and need for surgery were evaluated. Results A positive family history of IBD was noted in 216 patients with CD (7.0%) and in 238 patients with UC (6.7%). Of all patients, 167 consanguineous pairs in 146 families were identified. The crude concordance rate for IBD type was 82.6% with a kappa index of 0.656 [95% confidence interval (CI): 0.545-0.768, good concordance]. There was mild concordance for disease location in CD (kappa = 0.256; 95% CI: 0.007-0.505) and for the use of antitumor necrosis factor agents in UC (kappa = 0.354; 95% CI: -0.049-0.757). The concordance for IBD type and several phenotypes in first-degree relative pairs was better than that in the entire pairs. Conclusions Disease type and phenotypic characteristics of patients with familial IBD may be anticipated.