Renal-Limited Sarcoidosis Presenting as Acute Kidney Injury: A Biopsy-Guided Diagnostic Challenge

We report a case of a 72-year-old female presenting with vomiting and generalized weakness for two weeks. Laboratory evaluation revealed severe acute kidney injury with a serum creatinine of 12.4 mg/dL. Renal biopsy demonstrated granulomatous interstitial nephritis with non-caseating granulomas and occasional Schaumann bodies. Extensive evaluation excluded tuberculosis, drug-induced injury, infections, and autoimmune diseases. High-resolution CT chest showed no pulmonary involvement. In view of characteristic histomorphology and markedly elevated serum ACE levels, a diagnosis of renal-limited sarcoidosis was made. Treatment with oral prednisolone (0.5 mg/kg/day) resulted in significant improvement in renal function, with creatinine declining to 1.4 mg/dL on follow-up.