Figure 1728

Electron micrographs of mesangiocapillary glomerulonephritis (MCGN) type I (A) and type II (B). The histologic features of recurrence are the same as for the primary disease. In type II MCGN the ribbonlike band of electron-dense material within the glomerular basement membrane has been observed as early as 3 weeks after transplantation. Initially, the recurrence is focal but subsequently progresses to involve most of the capillary walls. Failing grafts frequently have segmental glomerular necrosis and extracapillary crescents. Making the diagnosis is not difficult when electron microscopy has been performed on the transplantation biopsy. In MCGN type I, electron-dense deposits first appear in the mesangium and subsequently in a subendothelial position. Mesangial cell interposition frequently is visible on electron microscopy, and on light microscopy the capillary walls appear thickened and show a double contour. The differential diagnosis is MCGN caused by acute or chronic transplantation glomerulopathy. Global changes, immune deposits, and increased mesangial cells, however, are rare in chronic transplantation glomerulopathy. Endocapillary proliferation and macrophages within capillary loops are important features of acute transplantation glomerulopathy, which usually are absent in recurrent MCGN [13].

Endothelial cell Basement membrane

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Capillary lumen

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Continuous band of electron-dense material B in basement membrane

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