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Most Frequent ClinicalPresentation Pathogenesis Light Microscopy Fluorescence Microscopy Electron Microscopy Poststreptococcal glomerulonephritis Acute nephritis Antibody mediated; circulating or planted antigen Diffuse proliferation; leukocytic infiltration Granular IgG and C3 in GBM and mesangium Subepithelial humps Goodpasture syndrome Rapidly progressive glomerulonephritis Anti-GBM COL4-A3 antigen Proliferation; crescents Linear IgG and C3; fibrin in crescents No deposits; GBM disruptions; fibrin Idiopathic RPGN Rapidly progressive glomerulonephritis Anti-GBM antibody Proliferation; focal necrosis; crescents Linear IgG and C3 No deposits Immune complex Granular IgG or IgA or IgM Deposits may be present ANCA-associated Negative or equivocal No deposits Membranous glomerulopathy Nephrotic syndrome In situ antibody-mediated; antigen unknown Diffuse capillary wall thickening Granular IgG and C3; diffuse Subepithelial deposits Minimal change disease Nephrotic syndrome Unknown, loss of glomerular polyanion; podocyte injury Normal; lipid in tubules Negative Loss of foot processes; no deposits Focal segmental glomerulosclerosis Nephrotic syndrome; non-nephrotic proteinuria Unknown, Ablation nephropathy Plasma factor (?); podocyte injury Focal and segmental sclerosis and hyalinosis Focal; IgM and C3 Loss of foot processes; epithelial denudation Membranoproliferative glomerulonephritis (MPGN) Type I Nephrotic syndrome (I) Immune complex (I) IgG + C3; C1q + C4 (I) Subendothelial deposits Mesangial proliferation; basement membrane thickening; splitting Dense deposit disease (MPGN Type II) Hematuria (II) Autoantibody: alternative complement pathway (II) C3 ± IgG; no C1q or C4 (II) Dense deposits Chronic renal failure IgA nephropathy Recurrent hematuria or proteinuria Unknown; see text Focal proliferative glomerulonephritis; mesangial widening IgA +/- IgG, IgM, and C3 in mesangium Mesangial and paramesangial dense deposits Chronic glomerulonephritis Chronic renal failure Variable Hyalinized glomeruli Granular or negative ANCA, antineutrophil cytoplasmic antibody; GBM, glomerular basement membrane; RPGN, rapidly progressive glomerulonephritis. all lobules of all glomeruli. There is also swelling of endothelial cells, and the combination of proliferation, swelling, and leukocyte infiltration obliterates the capillary lumens. There may be interstitial edema and inflammation, and the tubules often contain red cell casts. By immunofluorescence microscopy,there are granular deposits of IgG, IgM, and C3 in the mesangium and along the basement membrane. Although almost universally present, they are often focal and sparse. The characteristic electron microscopic findingsare discrete, amorphous, electrondense deposits on the epithelial side of the membrane, often having the appearance of "humps" ( Fig. 20-16C) , presumably representing the antigen-antibody complexes at the epithelial cell surface. Subendothelial and intramembranous deposits are also commonly seen, and mesangial deposits may be present. There is often swelling of endothelial and mesangial cells. Clinical Course. In the classic case, a young child abruptly develops malaise, fever, nausea, oliguria, and hematuria (smoky or cocoa-colored urine) 1 to 2 weeks after recovery from a sore throat. The patients exhibit red cell casts in the urine, mild proteinuria (usually less than 1 mg/day), periorbital edema, and mild to moderate hypertension. In adults, the onset is more likely to be atypical, with the sudden appearance of hypertension or edema, frequently with elevation of BUN. During epidemics caused by nephritogenic streptococcal infections, glomerulonephritis may be asymptomatic, discovered only on screening for microscopic hematuria. Important laboratory findings include elevations of antistreptococcal antibody (ASO) titers and a decline in the serum concentration of C3 and other components of the complement cascade and the presence of cryoglobulins in the serum. More than 95% of affected children eventually recover totally with conservative therapy aimed at maintaining sodium and water balance. A small minority of children (perhaps less than 1%) do not improve, become severely oliguric, and develop a rapidly progressive form of glomerulonephritis Figure 20-16Acute proliferative glomerulonephritis. A, Normal glomerulus. B, Glomerular hypercellularity is due to intracapillary leukocytes and proliferation of intrinsic glomerular cells. C, Typical electron-dense subepithelial "hump" and a neutrophil in the lumen. (Courtesy of Dr. H. Rennke, Brigham and Women's Hospital, Boston, MA.) TABLE 20-7-- Rapidly Progressive Glomerulonephritis (RPGN) Date: 2016-04-22; view: 852
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