Primary IgA nephropathy. Contrasting morphometric insight into glomerular and interstitial changes in younger and elderly patients.

Twelve patients with primary diffuse IgA nephropathy (IgAN) aged under 45 years (IgAN < 45), and eleven patients with this glomerulopathy aged over 45 years (IgAN > 45) for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available were examined quantitatively and compared with fifteen normal controls. Morphometric investigations were performed by means of a computer image analysis system to characterize quantitatively IgAN in patients over and below 45 years of age as well as to study whether changes in quantitatively analyzed glomeruli could correlate with hematuria, which is thought as the main renal symptom in this glomerulopathy. The study revealed that the mean values of 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 in both IgAN < 45 and IgAN > 45 groups increased in comparison with normal controls, most of them significantly. The comparison of these parameters between IgAN < 45 and IgAN > 45 groups showed that the mean values of total glomerular cells per total glomerular area and total glomerular cells per unit of glomerular area were significantly greater in IgAN < 45 group, but relative interstitial volume was significantly increased in IgAN > 45 patients. Moreover, there were significant positive correlations between total glomerular cells per unit of glomerular area and hematuria, but not between glomerular mesangium (% of total glomerular area) and hematuria in both IgAN < 45 and IgAN > 45 groups. In conclusion, we found evident quantitative differences between glomerular and interstitial parameters in younger and elderly patients. Although close relationship was observed between glomerular hypercellularity and the degree of hematuria in both younger and elder patients, this association is not clear and its pathogenesis remains to be shown.