Clinicopathological characteristics and outcomes of renal sarcoidosis: A series study of 18 patients from a single center.

INTRODUCTION: Sarcoidosis is characterized by non-caseating granulomatous inflammation in multiple organs. Renal involvement is rare, and granulomatous tubulointerstitial nephritis (GIN) is the predominant histologic feature. Renal sarcoidosis (RS) is usually diagnosed by exclusion, combining clinical and histological findings, and often remains misdiagnosed. This retrospective study aimed to describe the characteristics and prognosis of patients with RS in China.

METHODS: 18 patients with RS from a single center were enrolled, of whom 15 had biopsy-proven tubulointerstitial nephritis. Their clinicopathological features and renal outcomes were analyzed to understand this rare disease better.

RESULTS: 18 patients (14 male/4 female) were included in our study. The median eGFR was 30.36 (11.57, 60.14) ml/min/1.73m2. In 15 patients undergoing a renal biopsy, GIN was the most common pathological phenotype (66.67%). 17 patients had follow-up records, with a median follow-up of 24.07 (8.82, 60.90) months. One month after treatment, median estimated glomerular filtration rate (eGFR) increased significantly from 30.36 (11.57, 60.14) ml/min/1.73m2 to 58.53(39.35, 80.65) ml/min/1.73m2, and proteinuria decreased from 1.10 (0.69, 1.58) g/24h to 0.68 (0.52, 1.05) g/24h. No patients relapsed or developed end-stage renal disease.

CONCLUSION: RS is a rare but important cause of tubulointerstitial injury, with a favorable long-term prognosis if properly diagnosed and treated promptly.