Renal involvement in sarcoidosis: Histologic findings and clinical course

Renal failure in sarcoidosis is rare and data on its long-term outcome are scarce. To investigate the pattern of renal involvement in sarcoidosis, its clinical course and response to treatment in the long-term. A single-center retrospective study with review of renal biopsies and medical charts was performed. Between January 2005 and December 2016, seven patients with sarcoidosis underwent a kidney biopsy. This is equivalent to a frequency of 1.6% in a total of 434 biopsies from native kidney performed in our institution. All patients presented with renal failure. Five patients had granulomatous interstitial nephritis (GIN) and one patient each interstitial nephritis without granuloma and nephrocalcinosis. Three patients had concomitant glomerular disease: IgA nephropathy (n = 2), membranous and focal proliferative glomerulonephritis (n = 1). Most patients (n = 5) presented with hypercalcemia. All patients initially received oral prednisolone 1 mg/kg/day (n = 3) or 0.5 mg/kg/day (n = 4), respectively, with subsequent tapering or suspension. One patient was started on azathioprine after 18 months to spare steroids. After a mean follow-up of 59 months mean estimated glomerular filtration rate (eGFR) had improved from 19 ± 7 at presentation to 49 ± 16 mL/min. No patient required dialysis. All patients started on prednisolone 1 mg/kg/day developed transient diabetes mellitus while patients on 0.5 mg/kg/day did not. Renal function improvement did not differ between both treatment groups. GIN was the most common diagnosis in sarcoidosis patients with renal failure. Initial hypercalcemia was observed in the majority. Early steroid treatment lead to sustained renal function improvement.