Renal Sarcoidosis Mimicking Xanthogranulomatous Pyelonephritis.

A 70-year-old male patient underwent left-sided nephrectomy for signs and symptoms that were suggestive of xanthogranulomatous pyelonephritis (recurrent fever, swollen malfunctioning kidney, granulomatous inflammation in renal biopsy). Contralateral progression and workup for further symptoms finally established the diagnosis of extrapulmonary sarcoidosis. With corticosteroid and azathioprine treatment, renal function was preserved in the long term. Awareness of similarities in computed tomography imaging and histopathological findings of xanthogranulomatous pyelonephritis and renal sarcoidosis may prevent delayed diagnosis and inappropriate treatment of the latter.