IgA nephropathy presenting clinicopathological features of acute post-streptococcal glomerulonephritis

A 5-year-old Japanese girl was affected with acute nephritis. The patient had hypo-complementaemia and an elevation of anti-streptolysin O with positive throat culture of Group A streptococci. Four weeks after onset of the disease, serum complement level returned to normal, but proteinuria increased into the nephrotic range with a deterioration in renal function. Four weeks after onset, light microscopy of a renal biopsy showed diffuse endocapillary proliferation, and immunofluoroscopy revealed predominant IgA deposition in the mesangium. Electron microscopy showed electron dense deposits in the mesangial and subendothelial area, but subepithelial deposits were not found in the glomeruli. Histological diagnosis was IgA nephropathy, while her clinico-serological features were typical of acute post-streptococcal glomerulonephritis.

These results suggest that in some patients, IgA nephropathy may be triggered by streptococcal infection and misdiagnosed as acute post-streptococcal glomerulonephritis if renal histological examinations are not done.