Introduction:
Sarcoidosis is a multisystem disease characterized by non-caseating granulomatous inflammation. The most common organs involved are the lungs, lymph nodes, skin, and eyes, though it can affect any organ. Renal sarcoidosis is rare, and granulomatous interstitial nephritis (GIN) is the predominant histological feature. Renal sarcoidosis is usually diagnosed by exclusion with a combination of clinical and histological characteristics. Renal manifestations are varied and are a clinical challenge for clinicians requiring mandatory treatment, given the risk of development of renal failure. Renal sarcoidosis often remains misdiagnosed, and the incidence and prevalence of kidney involvement in sarcoidosis remain uncertain. This retrospective study aimed to describe the spectrum of renal manifestations, pathological characteristics and prognosis of patients with renal sarcoidosis.
Methods:
A retrospective single-center observational study included patients with renal sarcoidosis from the pool of patients between January 2010 and Aug 2024. Patients were identified using the database at the Department of Nephrology, Christian Medical College, Vellore, Tamil Nadu, India. Patients with confirmed sarcoidosis, according to the statement of the American Thoracic Society (ATS), the World Association of Sarcoidosis and Other Granulomatous Disorders (WASOG) and The European Respiratory Society were enrolled. We conducted the current study to analyze clinicopathological features, renal manifestations and outcomes of renal sarcoidosis.
Results:
An interim analysis was done on 90 patients (54 male/36 female, M/F ratio: 1.5) with renal sarcoidosis. Median estimated glomerular filtration rate (eGFR) was 35.56 ml/min/1.73m2. Elevated serum creatinine when diagnosed with sarcoidosis was found in 88 (97%) patients. Mild to moderately increased proteinuria was found in 54 (60%) patients. Severely increased proteinuria (>300 mg/gm) was found in 5 (5.55%) patients. Stage 4 or 5 chronic kidney disease (CKD) at presentation was detected in 60 (66.66%) patients. Fifteen (16.66%) patients had CKD 5 at diagnosis. Twenty-seven of 90 (30%) patients had hypercalcemia, of whom 27 (90%) patients had hypercalcemia-induced acute kidney injury at presentation. Three patients were found to have bilateral renal calculi on imaging at presentation. Two patients had obstructive uropathy with no obvious obstructive renal calculi on imaging. Three patients presented with rapidly progressive renal failure. Kidney biopsy of all three patients revealed granulomatous interstitial nephritis. Thirty (33.33%) patients presented with noncaseating granulomatous interstitial nephritis (GIN). Twelve (13.33%) patients showed acute interstitial nephritis (AIN) without granulomas, while three had chronic interstitial nephritis (CIN) without granulomas. Three patients had tubular microcalcific deposits, one of whom showed focal interstitial histiocyte aggregates without granulomas. Two patients showed arterionephrosclerosis with focal tuft atrophy. We found one patient each of IgA nephropathy (IgAN), focal segmental glomerulosclerosis (FSGS), and membranoproliferative glomerulonephritis (MPGN) on histopathological examination on diagnosis. Two patients had membranous nephropathy (MN) at presentation.
One patient who was diagnosed with sarcoidosis with granulomatous interstitial nephritis in 2008 at the age of 43 years reached ESRD in 2013. She was initiated on automated peritoneal dialysis and underwent deceased donor kidney transplantation in 2015. She had stable serum creatinine of 0.81 mg/dl with no proteinuria when she last followed up with us in May 2024.
Another patient who was a voluntary kidney donor for his son in 2013 presented with increased serum creatinine, interstitial pneumonitis and asymptomatic plaque on his upper lip in 2014. He was diagnosed with sarcoidosis based on imaging and histopathological examination showing non-necrotizing granulomatous inflammation. He was treated with oral steroids. He had stable renal function till he last followed up with us in 2017.
Conclusions:
Given multisystem disorder, patients with sarcoidosis should undergo screening for renal manifestations, including renal parameters and kidney biopsy, whenever applicable. The most common renal manifestation is noncaseating granulomatous interstitial nephritis associated with eGFR decline. Hypercalcemia with acute kidney injury is another common manifestation of sarcoidosis. Calcium nephrolithiasis and nephrocalcinosis may be the presenting feature. Uncommon manifestations of renal sarcoidosis include glomerular disease, obstructive uropathy and end-stage kidney disease. Kidney transplantation in patients with renal sarcoidosis has good prognosis. Voluntary kidney donor who manifested sarcoidosis with declining eGFR responded well to oral steroid treatment.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.