Acute tubulointerstitial nephritis following coronavirus disease 2019 mRNA vaccination: a pediatric case report.

Coronavirus disease 2019 (COVID-19) mRNA vaccines have been linked to various kidney adverse events including acute tubulointerstitial nephritis (ATIN). This report describes a 15-year-old female who developed persistent fever and fatigue 54 days after receiving her second dose of the BNT162b2 2 SARS-CoV-2 vaccine. She presented with elevated serum creatinine and urinary β2-microglobulin (β2MG) levels. Kidney biopsy revealed mononuclear infiltrate with some eosinophils, confirming the diagnosis of ATIN. Repeatedly positive lymphocyte transformation test results for the vaccine suggested a relationship between the vaccine and interstitial nephritis. Initially, treatment with prednisolone was effective. However, an increase in urinary β2MG level was observed 7 months later, and the introduction of mycophenolate mofetil (MMF) allowed for the gradual reduction and eventual cessation of prednisolone. This case represents one of the rare pediatric instances of ATIN following COVID-19 vaccination. MMF can be an effective alternative in corticosteroid-dependent cases.