Post-MRSA infection glomerulonephritis with marked Staphylococcus aureus cell envelope antigen deposition in glomeruli

A 48-year-old male developed massive proteinuria and renal dysfunction after pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) infection. Examination of a renal biopsy specimen by light microscopy showed severe mesangiocapillary proliferative glomerulonephritis with fibrocellular crescents. Immunofluorescence microscopy showed weak linear staining for immunoglobulin G (IgG), while both the peripheral and mesangial lesions stained for IgA and C3. Immunostaining for a possible antigen related to post-MRSA infection glomerulonephritis, using monoclonal antibody S1D6, revealed marked deposition of S.aureus cell envelope antigen in the glomeruli. Electron-dense deposits were observed in both the subendothelial and the mesangial areas. Focal subendothelial widening accompanied with monocytes or foam cell infiltration was also seen. The findings reflect a typical post-MRSA infection glomerulonephritis caused by S.aureus cell envelope antigen.