The significance of glomerular hypertrophy in focal segmental glomerulosclerosis

It is not clear whether glomerular hypertrophy is linked to the pathogenesis of human focal segmental glomerulosclerosis (FSGS). To probe the significance of glomerular hypertrophy in relation to development of FSGS, we studied 16 adults with primary FSGS by morphometry, and the findings were compared to age- and sex-matched subjects with minimal lesion. Mean glomerular volume (MGV), mesangial volume density, mesangial volume per glomerulus, and cortical interstitial volume density [Vv(int/cortex)] were significantly increased in the FSGS patients when compared to the minimal lesion patients. The increase in mesangial volume in FSGS was mainly due to expansion of mesangial matrix. In FSGS, MGV was related directly to % of glomeruli with glomerulosclerosis (r = 0.47, p < 0.05), to mesangial volume per glomerulus (r = 0.57, p < 0.01), and to Vv(int/cortex) (r = 0.47, p < 0.05). The percentage of glomerulosclerosis correlated directly with Vv(int/cortex) (r = 0.83, p < 0.0005), and with mesangial volume per glomerulus (r = 0.47; p < 0.05) in FSGS. Also, there was a direct relationship between Vv(int/cortex) and mesangial volume per glomerulus (r = 0.49; p < 0.05) in FSGS. Glomerular hypertrophy observed in our patients with primary FSGS was intercorrelated with the extent of glomerulosclerosis, mesangial expansion and interstitial fibrosis. Glomerular hypertrophy seems to be one of the morphological facets present in FSGS. Glomerular hypertrophy tends to coexist with FSGS rather than precede its development. Thus, in biopsies diagnosed with minimal lesion the presence of glomerular hypertrophy appears to be an indication that the coexistent FSGS lesions are undetected as a result of sampling problems.