Focal segmental glomerulosclerosis in idiopathic membranous glomerulonephritis : a clinico-pathological and stereological study

Background. The phenomenon of focal segmental glomerulosclerosis (FSGS) in idiopathic membranous glomerulonephritis (IMGN) has not been adequately studied. There is also a paucity of detailed glomerular morphometric and stereologic analyses data on renal biopsy in this association. Methods. Twenty-three (23) patients with IMGN and superimposed FSGS were compared to 35 patients with IMGN alone with respect to the clinical and laboratory features, light microscopic findings and stereologic parameters (glomerular cross-sectional area and estimated glomerular volume). Results. In the clinical parameters, patients with IMGNFSGS had a significantly higher incidence of hypertension, raised serum creatinine and microscopic haematuria. The mean 24-h urinary protein excretion was higher in the group with IMGN-FSGS (7.4 ± 1.36 g) as compared to IMGN alone (3.85 ± 0.7 g, P < 0.001, Mann–Whitney test). On light microscopy, biopsies with IMGN-FSGS frequently had mesangial hypercellularity and more extensive tubulointerstitial disease than those with IMGN alone. Stereological analysis showed that the non-sclerosed glomeruli in biopsies with IMGN-FSGS had a higher mean crosssectional area (185466.7 ± 32493.3 μ2) and higher estimated volume (855200 ± 152640 μ3) as compared to glomeruli in cases with IMGN alone (76000 ± 14719.2 μ2 and 576666.7 ± 131233.3 μ3, respectively). Conclusion. The present study is probably the first systematic analysis of stereologic parameters in renal biopsies of IMGN with FSGS. Our results objectively demonstrate the glomerular enlargement in the non-sclerosed glomeruli in cases of IMGN with FSGS. This detection of enlarged glomeruli may serve to alert the renal pathologist to the possibility of coexisting FSGS, which is a poor prognostic factor in IMGN.