Correlation between urinary protein fractions and histological features in IgA nephropathy

Urinary protein fractions and clinicopathological features in 80 patients with IgA nephropathy, who had mild proteinuria (0.60 +/- 0.35 g/day) less than 2 g/day, were analyzed. Urinary protein fractions was determined with SDS-polyacrylamide microgel electrophoresis (SDS-PAGE). The patterns on the densitogram of SDS-PAGE were divided into 4 groups, that is, normal pattern (Group I: N = 4), low molecular weight proteins (LMWP) predominant pattern (Group III: N = 29) and high molecular weight proteins (HMWP) excessive pattern (Group IV: N = 28). Histological changes were minor in majority of Group I but gradually increased in Group II, III and IV. Especially in Group IV, global sclerosis (78.6%; vs. Group II: p less than 0.01, vs. Group III: p less than 0.05), small crescent (57.1%; vs. Group II: p less than 0.05), adhesion (60.7%; vs. Group II: p less than 0.05), mesangial proliferation (96.4%; vs. Group II: p less than 0.01, vs. Group III: p less than 0.05) and tubulointerstitial degeneration (85.7%; vs. Group II and III: p less than 0.05) were most predominant. These results indicate that urinary protein fractions and histological changes appear to correlate closely in IgA nephropathy with mild proteinuria, and that marked HMWP is considered to be an early marker of glomerular damage in the prognosis of IgA nephropathy.