Carboplatin-related acute interstitial nephritis in a patient with pancreatic neuroendocrine tumor

Carboplatin is characterized by low nephrotoxicity, including acute tubular necrosis (ATN), compared to a conventional platinum complex due to its low accumulative property in the renal tubules. Therefore, there are extremely few reports of carboplatin-induced kidney injury and only one case has been histologically examined. Herein, we describe the case of a 53-year-old man who presented with acute kidney injury (AKI) that occurred after carboplatin administration and was diagnosed with biopsy-proven acute interstitial nephritis (AIN). To our knowledge, this is the second case report of carboplatin-related AIN. The patient was diagnosed with a pancreatic neuroendocrine tumor, and chemotherapy consisting of cisplatin and irinotecan was initiated. However, 1 week later, he was admitted to our institution with fever, fatigue and an increase in C-reactive protein (CRP) level. The chemotherapy regimen was altered to carboplatin and etoposide, but high fever occurred on the first day, and CRP re-elevation and AKI became apparent 9 days later. Renal biopsy revealed prominent inflammatory cell infiltration into the interstitium, which lead to the pathological diagnosis of AIN. On immunostaining for surface markers, CD3- and CD68-positive cells were found to be predominant, and CD20-positive cells were relatively few. Although the serum creatinine level increased to 6.81 mg/dL, it decreased to 1.43 mg/dL 15 days after steroid therapy. This case demonstrated that carboplatin-related kidney injury includes not only ATN but also AIN. Appropriate pathological diagnosis including renal biopsy and indications for steroid treatment should be carefully considered.