Study of lupus nephritis: its classification and the significance of subendothelial deposits.

This study describes the clinical and pathological characteristics of 74 patients with lupus nephritis classified according to renal biopsy findings using light, electron and immunofluorescent microscopy, and further, assesses the significance of subendothelial deposits in evaluating disease activity. In membranous lupus nephritis (14 cases), many cases showed normal renal function even with the nephrotic syndrome, although five cases had little or no urinary abnormalities. Glomerular cellular proliferation was very mild and subepithelial deposits with a few mesangial deposits were the main pathological alterations. Mesangial proliferative lupus nephritis (17 cases) clinically had very mild renal disease. Renal biopsies in this group revealed mesangial deposits with slight cellular proliferation. Although clinical features of mild diffuse proliferative lupus nephritis (16 cases) were similar to those of mesangial lupus nephritis, glomerular loop deposits were seen in addition to mesangial deposits. In moderate diffuse proliferative lupus nephritis (17 cases), renal function was slightly decreased, moderate proteinuria with haematuria were found, and C3 level was low. Renal biopsies showed active proliferative changes, and subendothelial deposits were frequently seen. In severe diffuse proliferative lupus nephritis (10 cases), the duration from onset of SLE to renal biopsy was short. Impairment of renal function, and nephrotic syndrome with haematuria and hypocomplementemia were frequent. Only three patients survived in this group. Renal biopsies demonstrated highly active proliferative and necrotizing changes, and electron microscopy showed massive subendothelial and mesangial deposits accompanied by subepithelial and intramembranous deposits. The amount of subendothelial deposits correlated with those of mesangial deposits and subepithelial deposits in the cases with diffuse proliferative lupus nephritis. Urinary protein loss and histologic activity showed statistically significant correlations with the amount of subendothelial deposits, but C3 levels and creatinine clearance revealed negative correlations with those deposits.