Abstract
An 87-year-old Japanese woman had chronic kidney disease due to hypertensive nephrosclerosis, with the serum creatinine （Cr） level having been stably around 1.5 mg / dL. Her primary care physician treated her for osteoporosis with an initial intravenous zoledronic acid （ZA）. After 12 days, she was admitted to our hospital with severe renal dysfunction （BUN: 74.9 mg / dL, Cr: 7.90 mg / dL）. The lab data also showed tubulointerstitial disorder and incomplete Fanconi syndrome. Because of dementia and other comorbidities, it was difficult to confirm the histological diagnosis with renal biopsy. The renal dysfunction and urinary findings had not been improved with hydration, and the inflammation with C-reactive protein （CRP） level around 12 mg / dL had persisted. Diagnostic treatment with glucocorticoid （methylprednisolone pulse therapy followed by daily intravenous administration of 40 mg methylprednisolone） rapidly ameliorated both renal dysfunction and inflammation. Tubulointerstitial disorders caused by ZA have been mostly reported as acute tubular necrosis. In this case, in spite of lack of histological diagnosis, the diagnosis of tubulointerstitial nephritis was highly probable because of the obvious therapeutic effects of glucocorticoid treatment. Therefore, this case suggests that tubulointerstitial nephritis should be included in the differential diagnosis when acute kidney injury accompanied by inflammation, otherwise unexplainable, occurs after ZA administration.
