IgA-dominant infection-related glomerulonephritis with NAPlr-positive tubulointerstitial nephritis

Infection-related glomerulonephritis (IRGN) is one of the most common causes of acute kidney injury (AKI). Positive glomerular staining of the nephritis-associated plasmin receptor (NAPlr) has been reported as a useful biomarker of IRGN. Although the infection can provoke acute tubulointerstitial nephritis (AIN), there are few reports of positive staining for NAPlr with AIN. We report a case of methicillin-sensitive Staphylococcus aureus (MSSA) infection-related nephritis complicated with AIN, which showed positive staining for tubulointerstitial NAPlr. The patient developed AKI and nephrotic syndrome during an intraperitoneal MSSA infection. A diagnosis of IRGN complicated by infection-related acute tubulointerstitial nephritis (IRAIN) was made based on glomerular endocapillary proliferation with tubulointerstitial infiltrating cells and tubular atrophy. Tubulointerstitial infiltrating cells were positive for NAPlr staining and plasmin activity. Treatment of the infection by antibiotics and drainage did not improve the AKI, but steroid administration improved that. NAPlr evaluation is a helpful tool for identifying causes of AIN during infection.