Autoimmune diseases in microscopic colitis: A Danish nationwide case–control study

Summary Background The association between autoimmune diseases and microscopic colitis remains uncertain. Aims To describe the association between autoimmune diseases and microscopic colitis by using a matched case–control design based on nationwide registry data. Methods All adult Danish patients with a diagnosis of microscopic colitis from 2001 to 2018 were identified from nationwide registries. Odds of autoimmune diseases were compared between cases with microscopic colitis and sex‐ and age‐matched controls from the background population in a 1:10 ratio and evaluated by logistic regression calculating odds ratios (OR) with 95% confidence intervals (CI) adjusted for comorbidity. Analyses were stratified according to sex, age and the subtypes of lymphocytic and collagenous colitis. Results We identified 15 597 cases with microscopic colitis and matched to 155 910 controls. In total, 3491 (22%) of patients with microscopic colitis had concomitant autoimmune disease compared to 16 521 (11%) of controls (OR, 2.46; 95% CI, 2.36‐2.56). Adjusting for comorbidities reduced the OR to 2.09 (95% CI, 2.01‐2.19). Analyses showed increased ORs with 16 different autoimmune diseases, particularly of gastrointestinal and endocrine origin, and connective tissue disorders. The highest ORs were for coeliac disease (OR = 10.15; 95% CI, 8.20‐12.6), Crohn’s disease (OR = 2.47; 95% CI, 2.10‐2.91) and ulcerative colitis (OR = 6.73; 95% CI, 6.20‐7.30). In stratified analyses younger age at diagnosis and collagenous colitis were associated with higher odds. Conclusion Using nationwide registry data, microscopic colitis was associated with a wide range of autoimmune diseases, especially of gastrointestinal origin. The results suggest an autoimmune predisposition to microscopic colitis. Using Danish nationwide data we demonstrated 15 597 cases with microscopic colitis and compared to 155 910 matches. In total (22%) of patients with microscopic colitis had concomitant autoimmune disease compared to (11%) matches, OR 2.09 (95% CI, 2.01‐2.19).Increased ORs with 16 different autoimmune diseases were detected.