Autoimmune diseases in primary sclerosing cholangitis and their first-degree relatives.

Background and aims: Primary sclerosing cholangitis (PSC) is linked to inflammatory bowel disease (IBD). However, there is limited overlap between IBD and PSC risk genes, but a stronger association between PSC and other autoimmune conditions. We aimed to assess the coexistence and familial association of autoimmune disorders in PSC, and the influence of autoimmune comorbidity on severe outcomes.

Approach and results: In a matched cohort study, 1378 individuals with PSC and 13,549 general population comparators and their first-degree relatives were evaluated. National registries provided data on diagnoses and outcomes (liver transplantation, hepatobiliary cancer, and liver-related death). The OR of autoimmune disease was estimated by logistic regression. The Fine and Gray competing risk regression estimated HRs for severe outcomes. The prevalence of non-IBD, non-autoimmune hepatitis, and autoimmune disease was 18% in PSC and 11% in comparators, OR: 1.77 (95% CI: 1.53-2.05). Highest odds were seen for celiac disease [OR: 4.36 (95% CI: 2.44-7.49)], sarcoidosis [OR: 2.74 (95% CI: 1.29-5.33)], diabetes type 1 [OR: 2.91 (95% CI: 2.05-4.05)], and autoimmune skin disease [OR: 2.15 (95% CI: 1.52-2.96)]. First-degree relatives of individuals with PSC had higher odds of developing IBD, autoimmune hepatitis, and any autoimmune disease than relatives of the comparators [OR: 3.25 (95% CI: 2.68-3.91); OR: 5.94 (95% CI: 2.82-12.02); OR: 1.34 (95% CI: 1.19-1.50)]. Autoimmune comorbidity in PSC was not associated with poorer outcomes [HR: 0.96 (95% CI: 0.71-1.28)].

Conclusions: Individuals with PSC and their first-degree relatives had higher odds of autoimmune disease compared to matched comparators. This finding provides validation for prior genetic discoveries at a phenotypic level. Autoimmune comorbidity did not impact severe outcomes.