Acute kidney injury caused by sarcoid granulomatous interstitial nephritis without extrarenal manifestations

Granulomatous interstitial nephritis (GIN) is one of the renal pathological manifestations of sarcoidosis. It is usually clinically silent, but may present occasionally as acute kidney injury (AKI). AKI caused by sarcoid GIN without extrarenal manifestations is extremely rare. We report a case of a 70-year-old man with a history of type 2 diabetes mellitus admitted with progressively worsening kidney function. The patient also exhibited anorexia, malaise and weight loss. Laboratory tests showed an elevated serum lysozyme level, but the serum angiotensin-converting enzyme (ACE) and serum calcium levels were normal. Increased uptake was evident only in kidney on gallium 67 scintigraphy. Although typical organ involvement of sarcoidosis was not evident, a renal biopsy showed granulomatous interstitial nephritis with non-caseating granulomas. No medications had been added in the 3 years preceding renal function deterioration. Following a bronchoalveolar lavage that revealed a high CD4:CD8 ratio, and a skin test that showed negative for tuberculin, a diagnosis of renal sarcoidosis was established. On diagnosis, oral prednisolone was initiated and renal function improved. The anorexia and malaise also disappeared. This is the extremely rare case of AKI caused by sarcoid GIN without extrarenal manifestations or elevated serum ACE level.