Two cases of IgA-dominant post-infectious glomerulonephritis

Abstract

Post-infectious glomerulonephritis (PIGN) is predominantly a childhood illness which is becoming less common in developed countries. Streptococcal infections precede the majority of cases, in which immunofluorescence typically demonstrates mesangial and capillary loop IgG and C3. IgA-dominant PIGN is more recently described and most commonly follows Staphylococcal infections. Histopathology and electron microscopy findings are often similar to Streptococcal-associated PIGN, however IgA is by definition the dominant (or co-dominant) immunoglobulin present. Two cases of IgA-dominant PIGN are reported here. In both cases methicillin-susceptible Staphylococcus aureus (MSSA) infection preceded the development of haematuria/proteinuria. The first case is a 60-year-old woman, with reduced C3/C4 and mildly elevated creatinine. Renal biopsy immunofluorescence, histopathology and electron microscopy findings were consistent with IgA-dominant PIGN. The second case is a 68-year-old woman with elevated creatinine, with normal C3/C4. On histopathology, some glomeruli showed mild mesangial hypercellularity and endocapillary proliferation with focal segmental necrosis and small/early crescents. Electron microscopy showed mostly mesangial changes, with some capillary damage but no hump-like subepithelial or subendothelial deposits. Immunofluorescence showed mesangial IgA and C3 deposits, with IgA in some capillary loops. Features were not entirely typical of PIGN, however in the clinical context were consistent with IgA-dominant PIGN. These cases display the pathological variation that may occur in IgA-dominant PIGN.