Renal biopsy findings in Wegener's granulomatosis: segmental necrotizing glomerulonephritis with glomerular thrombosis.

The clinicopathologic features of 14 patients with documented Wegener's granulomatosis (WG), with a detailed analysis of renal biopsy findings, are presented. The characteristic renal lesion found in all initial and in three of eight follow-up biopsies was segmental necrotizing glomerulonephritis (SNGN). The SNGN was generally focal and involved more than 60 per cent of the glomeruli in only two specimens. Light microscopic evidence of glomerular thrombosis, with or without necrosis, was found in 60 per cent of the biopsies. By immunofluorescence fibrin was demonstrated in 54 per cent of the biopsy specimens with "acute" SNGN, while 36 per cent of the specimens lacked both IgG and C3. Electron microscopy showed fibrin(oid) deposition with variable platelet activation associated with mesangionecrosis (two specimens) and peripheral glomerular basement membrane fragmentation/dissolution (three specimens). Rare discrete intramembranous (four specimens) and mesangial/subendothelial (one specimen) dense deposits were identified, but these deposits were associated with necrosis in only two biopsies. These findings fail to demonstrate an immune complex pathogenesis for the SNGN and suggest that glomerular thrombosis and necrosis are the primary findings in WG.