Drug Reaction Causing Acute Tubulointerstitial Nephritis: A Molecular Mistake

Kidney diseases can affect different kidney structures, namely, the glomerulus, the tubules, and the interstitium. Acute tubulointerstitial nephritis (ATIN) affects both the tubules and the interstitium, initially through epithelial damage that can progress to interstitial fibrosis and tubular atrophy. There are different mechanisms that can produce ATIN, and most of them involve a renal immune response. The case involves a 53-year-old woman with breast cancer undergoing chemotherapy and pembrolizumab who was concurrently receiving a proton pump inhibitor and antibiotic therapy for an Escherichia coli urinary tract infection. She presented with persistent acute renal injury. Initial laboratory and imaging investigations did not reveal significant abnormalities. A kidney biopsy was performed, which demonstrated histopathological findings consistent with ATIN. Corticosteroid therapy was initiated, resulting in gradual improvement of renal function. This case aims to demonstrate the complexity of managing polymedicated patients and also shows the importance of timely diagnosis and prompt removal of the etiological agent.