Kidney outcomes and prognostic factors in biopsy-proven kidney sarcoidosis: a nationwide multicenter cohort study

Abstract Background Renal sarcoidosis is a rare manifestation of systemic sarcoidosis. Evidence guiding management remains limited. We aimed to characterize clinical and histopathological features, renal outcomes and predictors of recovery and relapse in patients with renal sarcoidosis. Methods In this retrospective, multicenter observational study across hospitals affiliated with the Spanish Group for the Study of Glomerular Diseases, we included patients with biopsy-confirmed renal sarcoidosis and ≥ 6 months of follow-up. Primary outcomes were renal recovery (defined as > 50% improvement in estimated glomerular filtration rate) and disease relapse (renal or extrarenal). Secondary outcomes included progression to end-stage kidney disease (ESKD) and treatment-related complications. Results Sixty patients with a mean age of 56.8 years were included. Tubulointerstitial involvement predominated (80%), with granulomatous interstitial nephritis in 56.7%, while 23.3% exhibited glomerular disease. Patients with interstitial-only patterns achieved more frequently renal recovery at 12 months compared with those with glomerular involvement (65.9% vs. 20%, P = 0.013). Intravenous corticosteroid pulses were associated with faster renal improvement in our cohort, although it should be interpreted cautiously because of potential indication bias. Higher oral corticosteroid doses, prolonged high-dose exposure, or slower tapering strategies did not improve renal outcomes and were associated with increased complications. Over a median follow-up of 36 months, 38.3% of patients experienced relapse, and 6.7% of patients progressed to ESKD. Conclusions Renal sarcoidosis exhibits heterogeneous presentations but substantial potential for renal recovery, particularly in patients with granulomatous interstitial nephritis. These findings may support further investigation of pathology-informed treatment strategies aimed at reducing corticosteroid exposure. Prospective studies are needed to define optimal treatment strategies.