Minimal change disease and idiopathic focal segmental glomerulosclerosis in adults. A quantitative study

Fifteen renal biopsy specimens from adult patients with minimal change disease (MCD) and fifteen with idiopathic focal segmental glomerulosclerosis (FSGS) for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available were examined quantitatively. As a control 6 biopsy and 9 autopsy specimens of the normal kidneys were used. Morphometric investigations were performed by means of a computer image analysis system to evaluate whether morphometric analysis may be helpful in morphological differential diagnosis of MCD and FSGS in adults as well as to study whether serum creatinine and changes in quantitatively analyzed glomeruli could correlate with the interstitial fibrosis. The morphometric comparisons of the glomeruli and renal interstitial tissue in patients with FSGS, MCD and controls revealed that the mean values of total glomerular area, total glomerular cells per total glomerular area, total glomerular cells per unit of glomerular area, mesangium (% of total glomerular area) and relative interstitial volume were increased in both MCD and FSGS patients in comparison with normal controls, most of them significantly in FSGS group. Furthermore, in FSGS the mean values of total glomerular area, total glomerular cells per total glomerular area and relative interstitial volume were significantly higher than those of the minimal lesion group. In FSGS there were significant positive correlations between interstitial volume and serum creatinine (r = 0.64, p < 0.005), between interstitial volume and glomerular mesangium (r = 0.75, p < 0.002) and between total glomerular area and serum creatinine (r = 0.54, p < 0.05). However, correlation between interstitial volume and total glomerular cells per unit of glomerular area, similarly like all correlations in MCD, was weak and not significant (r = 0.49, p-NS). Our morphometric data confirm that glomerular hypertrophy and the extent of interstitial fibrosis may be a valuable predictor of unfavorable evolution of FSGS as well as may be helpful in the differential diagnosis of MCD and FSGS in the elderly. We suggest, that quantitative analysis of these parameters is extremely useful in early cases of FSGS when sclerotic changes involve rather juxtamedullary glomeruli and can be misdiagnosed with MCD by light and electron microscopy.