FIGURE 2-15 (see Color Plate)

Light, immunofluorescent, and electron microscopy in membranous glomerulonephritis. Membranous glomerulonephritis is an immune complex-mediated glomerulonephritis, with the immune deposits localized to subepithelial aspects of almost all glomerular capillary walls. Membranous glomerulonephritis is the most common cause of nephrotic syndrome in adults in developed countries. In most instances (75%), the disease is idiopathic and the

antigen(s) of the immune complexes are unknown. In the remainder, membranous glomerulonephritis is associated with well-defined diseases that often have an immunologic basis (eg, systemic lupus erythematosus and hepatitis B or C virus infection); some solid malignancies (especially carcinomas); or drug therapy, such as gold, penicillamine, captopril, and some nonsteroidal anti-inflammatory reagents. Treatment is controversial.

The changes by light and electron microscopy mirror one another quite well and represent morphologic progression that is likely dependent on duration of the disease. A, At all stages immuno-fluorescence discloses the presence of uniform granular capillary wall deposits of immunoglobulin G and complement C3. B, In the early stage the deposits are small and without other capillary wall changes; hence, on light microscopy, glomeruli often are normal in appearance. C, On electron microscopy, small electron-dense deposits (arrows) are observed in the subepithelial aspects of capillary walls. D, In the intermediate stage the deposits are partially encircled by basement membrane material. E, When viewed with periodic acid-methenamine stained sections, this abnormality appears as spikes of basement membrane perpendicular to the basement membrane, with adjacent nonstaining deposits. Similar features are evident on electron microscopy, with dense deposits and intervening basement membrane (D). Late in the disease the deposits are completely surrounded by basement membranes and are undergoing resorption.

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