Undiagnosed renal sarcoidosis in a patient with chronic interstitial nephritis

A 53-year-old female was admitted to hospital, with acute elevation of SCr and hypercalcemia, on a 5-year history of chronic interstitial nephritis and stage III chronic kidney disease (CKD). Extensive workup failed to yield a definitive diagnosis concerning the cause of the disorder. Intense uptake of ¹⁸F-FDG in the spleen and liver was detected by PET/CT imaging with negative angiotensin-converting enzyme (ACE) in serum. The spleen and the hypermetabolism nodules of the liver were resected for histopathologic examination and turned out to be noncaseating granulomas, likely sarcoidosis. Combined with clinical features, the final diagnosis for this patient was sarcoidosis, involving the kidneys, spleen, liver, and lungs.