Acute kidney injury due to renal sarcoidosis during etanercept therapy: a case report and literature review.

We herein report a case of renal sarcoidosis presenting as acute kidney injury (AKI) during treatment with etanercept for rheumatoid arthritis. Blood tests showed a high level of angiotensin-converting enzyme and a renal biopsy demonstrated non-caseating granulomatous tubulointerstitial nephritis. The administration of high-dose steroid therapy (1 mg/kg) and discontinuation of etanercept resulted in an improvement in the patient's renal function. Although renal sarcoidosis induced by anti-tumor necrosis factor (TNF) therapy is an extremely rare manifestation, this case suggests that renal sarcoidosis should be considered in the differential diagnosis of AKI in patients receiving anti-TNF therapy, as providing an early diagnosis and treatment is important for preventing irreversible renal impairment.