Renal damage in systemic lupus erythematosus with normal renal function.

Renal biopsies were performed on 12 patients with definite systemic lupus erythematosus (SLE) with normal renal function. Three had had previous nephropathy which responded to treatment, with return of urinalysis and function to normal. Specimens were studied using light microscopy (LM), immunofluorescence (IF), and electron microscopy (EM). Mild to moderate abnormalities were found in all patients. Changes by LM (primarily hypercellularity) were found in 11 specimens (no glomeruli were obtained in one) and classified as inactive. IF studies were positive in eight of the 12 biopsies with either focal or diffuse distribution of IgG, IgM, and/or C3. EM changes were observed in all cases and were of mild to moderate severity. They included focal to multifocal glomerular hypercellularity, basement membrane thickening, foot process fusion, and mesangial and intramembranous electron dense deposits. No subepithelial or subendothelial deposits were found. Microtubular structures were present in three specimens. These data suggest that careful study of renal biopsy specimens may reveal evidence of kidney involvement in all patients with SLE.