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Subepithelial electron-dense deposits in proliferative glomerulonephritis of systemic lupus erythematosus
Abstract:
Subepithelial electron-dense deposits (SED) were found in the renal biopsies of 36 of 59 patients with systemic lupus erythematosus (SLE). The SED were divided into two groups based on their ultrastructural appearance and distribution within the glomeruli. Type I SED were regular in size and shape, had a homogeneous electron density and a diffuse distribution within the glomeruli, and involved all of the glomeruli in the biopsy. In contrast, the type II SED were irregular in size and shape, tended to be quite large, and had variable electron density. They were present in reduced numbers in involved capillary loops, and they were absent from other loops within the same glomerulus. Type I SED were seen in cases of membranous SLE glomerulonephritis (GN), and type II SED were associated with severe proliferative SLE GN. Although the patients with proliferative GN had more active urinary sediments at the time of biopsy than did the patients with membranous GN, the mean serum creatinine and urinary protein excretion were not significantly different in the two groups. The mean followup was almost twice as long for the membranous compared to the proliferative lesions (33.70 months +/- SE 7.96 vs. 16.78 +/- 4.21), but at the end of the study, mean renal function was better preserved in patients with proliferative GN (2.13 mg/dl +/- SE 0.49). As a group, patients with type I SED had mild serologic abnormalities compared to patients with type II SED. In contrast the abnormal serologies of the patients with type II SED were not significantly different from patients with proliferative SLE GN in general. The results suggest that the heterogeneous morphology of SED may reflect different pathogenetic mechanisms responsible for their formation. When focal and segmental SED (type II) are seen in proliferative SLE GN, they should be interpreted with caution, for they have very different clinical, prognostic, and therapeutic implications from type I SED.