Acute Interstitial Nephritis Induced by Pemetrexed in a Patient with Metastatic Adenocarcinoma of the Lung

Introduction: Acute interstitial Nephritis (AIN) is one of the underrecognized causes of acute kidney injury, mostly caused by Medications, although systemic illness and infections are fairly common, Prompt identification is crucial in order to provide appropriate therapy and prevent irreversible consequences. Case Description: A 62-year-old male with a history of Metastatic adenocarcinoma of the Lung (post-resection), HTN, CKD-g3a, A2, Asthma, DVT, CAD, HLD, Depression, and Crohn’s disease, presented with watery diarrhea and abdominal pain. Had been on a maintenance Pemetrexed following the initial response to Pemetrexed/Carboplatin adjuvant chemotherapy. Three weeks prior, treated with 7 days of Cefpodoxime and Metronidazole for sigmoid colitis. He developed moderate AKI that failed to respond to conservative management. Remained Hemodynamically stable, did not get recent contrast studies, no recent history of NSAIDs use, Diuretics were held to avoid further hypovolemia, Creatinine: peaked at 3.3 mmol/L baseline was 1.4-1.7 mmol/L, FeNA>2%, indicating tubular damage, urine showed eosinophils, Kidney US did not show evidence of obstructive uropathy, due to lack of renal recovery, Kidney Biopsy was performed and showed Moderately active interstitial Nephritis thought to be from Pemetrexed. Received tapering dose of Prednisone over 10 weeks, and chemotherapy was ceased with improvement of the creatinine levels and stabilized at 2.5 mmol/L His adenocarcinoma showed mild metabolic progression through PET scanning, yet no overt disease progression. Discussion: Pemetrexed is a recognized cause of ATN-induced renal dysfunction, to our knowledge it is rarely associated with acute interstitial nephritis (AIN). In this case, prior antibiotic use confounded the presentation, yet the patient exhibited progressive renal impairment with each Pemetrexed cycle and had a history of Pemetrexed-induced dermatitis, raising suspicion for drug-induced AIN. This case emphasizes the need for clinicians to consider Pemetrexed as a potential cause of AIN and further research is needed to stress on it’s nephrotoxic effects.