Urolithiasis is associated with an increased risk of sarcoidosis in a cohort in Sweden

<bold>Introduction:</bold> Disturbed calcium metabolism is associated with a severe sarcoidosis phenotype and urolithiasis made up of calcium oxalate could be an early sign for undiagnosed disease. It is unknown whether urolithiasis is more common before sarcoidosis compared to the general population. <bold>Aim:</bold> To investigate whether urolithiasis is associated with sarcoidosis and whether the association differs by sarcoidosis severity. <bold>Methods:</bold> Swedish population-based nationwide registers were used to conduct a case-control study. Adults with newly diagnosed sarcoidosis were matched to general population controls 10:1 on age, sex and region. Diagnoses of urolithiasis were collected from the Patient Register before sarcoidosis diagnosis. Sarcoidosis cases were classified as severe if they received treatment within three months of their diagnosis. Odds ratios (OR) and 95%CI of sarcoidosis associated with urolithiasis were estimated using conditional logistic regression models. <bold>Results:</bold> 11218 sarcoidosis cases and 124752 controls were included. At sarcoidosis diagnosis 3.2% of cases had a history of urolithiasis, compared to 2.0% of controls. A total of 3641 cases (32.5%) received treatment at diagnosis. The OR of sarcoidosis associated with urolithiasis was 1.69 (95%CI 1.37, 2.08) and did not differ by sarcoidosis severity. <bold>Conclusion:</bold> Urolithiasis is associated with a 69% increased risk of sarcoidosis. Our results indicate that urolithiasis can be a sign to facilitate early detection.