Concordance of phenotypic characteristics among patients with familial Crohn's disease in China.

Objectives: Familial Crohn's disease (CD) accounts for approximately 1.5%-22.5% of all CD cases worldwide. We aimed to assess the concordance in disease subtype and phenotypic features among patients with CD and their relatives based on data from a large, well-characterized, referral center-based cohort in China.

Methods: A retrospective study was conducted on patients with familial CD who were admitted to the Sixth Affiliated Hospital of Sun Yat-sen University between January 2012 and June 2022. We analyzed the disease characteristics and performed a concordance analysis within the same family among patients with familial CD.

Results: Among 5150 patients, 70 (1.4%) had a family history of Crohn's disease. The median age of the patients at initial diagnosis did not differ significantly between the probands and successors of family members with CD (p = 0.25). At the initial diagnosis, 54 first-degree relatives showed moderate concordance in age (κ = 0.50) and disease location (κ = 0.44). At the last follow-up visit, all family members and first-degree relatives showed good concordance in upper gastrointestinal involvement (κ = 0.67 and 0.62) and stricturing or penetrating behavior (κ = 0.69 and  0.77), respectively. Patients with familial CD within the same family showed moderate agreement regarding anti-tumor necrosis factor α monoclonal antibody use and treatment efficacy (κ = 0.44 and 0.42) and mild agreement regarding the efficacy and adverse reactions of thiopurine (κ = 0.26 and 0.35).

Conclusions: The proportion of patients with familial CD in China may be relatively low. The consistency of certain disease features in familial CD may be associated with the degree of kinship and convergence with longer follow-up duration.