Membranoproliferative Glomerulonephritis

FIGURE 2-18 (see Color Plate)

Light, immunofluorescence, and electron microscopy in membranoproliferative glomerulonephritis type I. In these types of immune complex-mediated glomerulonephritis, patients often exhibit nephrotic syndrome accompanied by hematuria and depressed levels of serum complement C3. The morphology is varied, with at least three pathologic subtypes, only two of which are at all common. The first, known as membranoproliferative (mesangiocapillary) glomerulonephritis type I, is a primary glomerulopathy most common in children and adolescents. The same pattern of injury may be observed during the course of many diseases with chronic antigenemic states; these include systemic lupus erythematosus and hepatitis C virus and other infections. In membranoproliferative glomerulonephritis type I, the glomeruli are enlarged and have increased mesangial cellularity and variably increased matrix, resulting in lobular architecture. The capillary walls often are thickened with double contours, an abnormality resulting from peripheral migration and interposition of mesangium (A). Immunofluorescence discloses granular to confluent granular deposits of C3 (B), immunoglobulin G, and immunoglobulin M in the peripheral capillary walls and mesangial regions. The characteristic finding on electron microscopy is in the capillary walls. C, Between the basement membrane and endothelial cells are, in order inwardly: (1) epithelial cell, (2) basement membrane, (3) electron-dense deposits, (4) mesangial cell cytoplasm, (5) mesangial matrix, and (6) endothelial cell. Electron-dense deposits also are in the central mesangial regions. Subepithelial deposits may be present, albeit typically in small numbers. The electron-dense deposits may contain an organized (fibrillar) substructure, especially in association with hepatitis C virus infection and cryoglobulemia.

FIGURE 2-19 (s

Plate)

FIGURE 2-19 (s

Light, immunofluorescence, and electron microscopy in membra-noproliferative glomerulonephritis type II. In this disease, also known as dense deposit disease, the glomeruli may be lobular or may manifest only mild widening of mesangium. A, The capillary walls are thickened, and the basement membranes are stained intensely positive periodic acid-Schiff reaction, with a refractile appearance. B, On immunofluorescence, complement C3 is seen in all glomerular capillary basement membranes in a coarse linear pattern. With the use of thin sections, it can be appreciated that the linear deposits actually consist of two thin parallel lines. Round granular deposits are in the mesangium. Coarse linear deposits also are in Bowman's capsule and the tubular basement membranes. C, Ultrastructurally, the glomeru-lar capillary basement membranes are thickened and darkly stained; there may be segmental or extensive involvement of the basement membrane. Similar findings are seen in Bowman's capsule and tubular basement membranes; however, in the latter, the dense staining is usually on the interstitial aspect of that structure. Patients with dense deposit disease frequently show isolated C3 depression and may have concomitant lipodystrophy. These patients also have autoantibodies to the C3 convertase enzyme C3Nef.

Plate)

0 0

Post a comment