Evidence for nephrolithiasis preceding sarcoidosis diagnosis: findings from a Swedish case-control study.

BACKGROUND: Patients with sarcoidosis have an increased risk for calcium metabolism disturbances, such as hypercalcemia and hypercalciuria. Previous studies suggest that nephrolithiasis (stone formation in the renal and ureter, often caused by dysregulated calcium balance) may occur long before sarcoidosis diagnosis and may be an early sign of not-yet-diagnosed sarcoidosis. We hypothesized that a history of nephrolithiasis is associated with future risk of sarcoidosis. METHODS: In this population-based matched case-control study, we included individuals with sarcoidosis and matched general population controls and identified those with a history of nephrolithiasis in Swedish nationwide registers. Patients with sarcoidosis who received treatment within three months of their sarcoidosis diagnosis were classified as severe. Nephrolithiasis severity was defined based on the need for intervention, multiple stones and early onset. Conditional logistic regression models estimated adjusted odds ratios with 95% confidence intervals (OR; 95%CI). RESULTS: A total of 10,904 sarcoidosis patients and 99,211 general population controls were included. At sarcoidosis diagnosis, 4.5% of patients had a history of nephrolithiasis compared to 2.6% of controls. Nephrolithiasis was associated with a 61% increased odds of sarcoidosis (adjusted OR = 1.61; 95%CI 1.46-1.78). The OR of severe sarcoidosis associated with a history of severe nephrolithiasis was 1.35 (95%CI 0.58-3.16). CONCLUSIONS: These findings indicate that nephrolithiasis might be an early sign of sarcoidosis in a subset of patients.