A case of post-pneumococcal acute glomerulonephritis with glomerular depositions of nephritis-associated plasmin receptor

We report the case of a 12-year-old girl who was referred to our hospital with anuria associated with pneumonia. On admission, the patient's blood test results revealed severe renal failure, hypoproteinemia, and hypocomplementemia. Her urinalysis results revealed hematuria, proteinuria, and a positive titer for Streptococcus pneumoniae. S. pneumoniae was also detected in her sputum and blood cultures. The patient was diagnosed with post-pneumococcal acute glomerulonephritis (AGN) with acute renal failure. A renal biopsy demonstrated the infiltration of neutrophils and mononuclear cells into capillary loops. Immunofluorescence studies showed dominant-positive deposition of C3c along the capillary loops and nephritis-associated plasmin receptor (NAPlr) depositions in the mesangial area and capillary loops. Electron microscopy revealed dense deposits in the glomerular basement membrane without a hump in the subepithelial area. These findings were consistent with endocapillary proliferative glomerulonephritis. AGN associated with pneumococcal infection is very rare. This case suggests that NAPlr is the causative antigen not only of post-streptococcal AGN, but also of post-pneumococcal AGN. To our knowledge, this is the first report that shows a relationship between post-pneumococcal AGN and NAPlr depositions in the glomeruli.