An uncommon culprit: PPI-induced acute tubulointerstitial nephritis in a teenager.

Proton pump inhibitor (PPI)-induced acute tubulointerstitial nephritis (ATIN) is rarely recognized in children. A 16-year-old boy presented with a 2-month history of vomiting, abdominal pain, and weight loss and had received PPIs repeatedly. He had elevated creatinine, metabolic acidosis, sterile pyuria, glucosuria, and markedly increased urine β2-microglobulin. Ultrasound showed enlarged echogenic kidneys. Despite hydration, kidney function did not improve. Kidney biopsy revealed T lymphocyte-predominant tubulointerstitial inflammation with eosinophils, consistent with hypersensitivity-mediated ATIN due to PPI use. He recovered fully with corticosteroids and cessation of PPI use. Concurrent Helicobacter pylori gastritis was treated with a PPI-free eradication regimen. This case highlights the importance of considering PPI-associated ATIN in unexplained pediatric AKI.