BACKGROUND: Sarcoidosis is a multi-system disorder characterised by non-caseating granulomas. Coexistence of sarcoidosis with immune-mediated and chronic inflammatory diseases has been described in case series. However, the coexistence of two different diseases in individuals can occur by chance, even if each of the diseases is rare. AIM: To determine whether sarcoidosis necessitating hospital admission or day-case care coexists with a range of immune-mediated and chronic inflammatory diseases more commonly than expected by chance. DESIGN: Analysis of an epidemiological database of hospital admission and day-case statistics, spanning 30 years. RESULTS: 1510 patients with sarcoidosis were identified (mean age 44 years, median follow-up 19 years) who had been admitted to hospital or day-case care. Significant associations in the sarcoidosis cohort were identified with systemic lupus erythematosus (odds ratio (OR) 8.3; 95% CI 2.7 to 19.4), autoimmune chronic hepatitis (OR 6.7; 95% CI 1.8 to 17.1), multiple sclerosis (OR 3.3; 95% CI 1.7 to 5.6), coeliac disease (OR 3.1; 95% CI 1.01 to 7.3), thyrotoxicosis (OR 2.5; 95% CI 1.4 to 4.0), myxoedema (OR 2.2; 95% CI 1.2 to 3.7) and ulcerative colitis (OR 2.1; 95% CI 1.1 to 3.7). Weaker associations were found for diabetes mellitus with a first admission aged 30-49 years (OR 2.9; 95% CI 2.1 to 4.0) or age >50 (OR 1.7; 95% CI 1.2 to 2.3), but not for people age <30. No significant association with Crohn's disease (OR 1.52; 95% CI 0.61 to 3.14) or primary biliary cirrhosis (OR 3.75; 95% CI 0.77 to 11.0),was found. When all immune-mediated and chronic inflammatory diseases for which associations were sought were combined, the overall rate ratio associated with sarcoidosis was 2.2 (95% CI 1.9 to 2.6). CONCLUSION: This study adds epidemiological evidence to information from clinical reports that there is a connection between sarcoidosis and other immune-mediated and chronic inflammatory diseases
