Characteristics of SLE of kidney is
Ref Robbins 9/e p224 Kidneys. Kidney involvement is one of the most impoant clinical features of SLE, with renal failure being the most common cause of death. The focus here is on glomerular pathology, although interstitial and tubular lesions are also seen in SLE. The pathogenesis of all forms of glomerulonephritis in SLE involves deposition of DNA-anti-DNA complexes within the glomeruli. These evoke an inflammatory response that may cause proliferation of the endothelial, mesangial, and/or epithelial cells and, in severe cases, necrosis of the glomeruli. Although the kidney appears normal by light microscopy in 25% to 30% of cases, almost all cases of SLE show some renal abnormality if examined by immuno- fluorescence and electron microscopy. According to the current International Society of Nephrology/Renal Pathol- ogy Society morphologic classification, there are six patterns of glomerular disease in SLE (none of which is specific to the disease): class I, minimal mesangial lupus nephritis; class II, mesangial proliferative lupus nephritis; class III, focal lupus nephritis; class IV, diffuse lupus nephritis; class V, membra- nous lupus nephritis; and class VI, advanced sclerosing lupus nephritis. * Minimal mesangial lupus nephritis (class I) is rarely encountered in renal biopsies. Immune complexes are present in the mesangium, but there are no concomitant structural alterations detectable by light microscopy. * Mesangial proliferative lupus nephritis (class II) is seen in 10% to 25% of cases and is associated with mild clinical symptoms. Immune complexes deposit in the mesangium, with a mild to moderate increase in the mesangial matrix and cellularity. * Focal lupus nephritis (class III) is seen in 20% to 35% of cases. Lesions are visualized in fewer than half the glomeruli, and they may be segmentally or globally distrib- uted within each glomerulus. Active lesions are character- ized by swelling and proliferation of endothelial and mesangial cells, infiltration by neutrophils, and/or fibrinoid deposits with capillary thrombi (Fig. 4-18, A). The clinical presentation may range from only mild microscopic hema- turia and proteinuria to a more active urinary sediment with red blood cell casts and acute, severe renal insufficiency. * Diffuse lupus nephritis (class IV) is the most serious form of renal lesions in SLE and is also the most commonly encountered in renal biopsies, occurring in 35% to 60% of patients. It is distinguished from focal lupus nephritis (class III) by involvement of half or more of glomeruli. Most of the glomeruli show endothelial and mesangial prolifera- tion, leading to diffuse hypercellularity of these structures (Fig. 4-18, B) and producing in some cases epithelial crescents that fill Bowman's space. When extensive, sub- endothelial immune complexes create a circumferential thickening of the capillary wall, resembling rigid "wire loops" on routine light microscopy (Fig. 4-18, C). Electron microscopy reveals prominent electron-dense subendo- thelial immune complexes (between endothelium and basement membrane) (Fig. 4-18, D), but immune com- plexes are also usually present in other pas of the capil- lary wall and in the mesangium. Immune complexes can be visualized by staining with fluorescent antibodies directed against immunoglobulins or complement, result- ing in a granular fluorescent staining pattern (Fig. 4-18, E). In due course, glomerular injury may give rise to scarring (glomerulosclerosis). Most affected patients have hematu- ria with moderate to severe proteinuria, hypeension, and renal insufficiency. * Membranous lupus nephritis (class V) occurs in 10% to 15% of cases and is the designation for glomerular disease characterized by widespread thickening of the capillary wall due to deposition of subepithelial immune complexes. Membranous glomerulonephritis associated with SLE is very similar to that encountered in idiopathic membranous nephropathy (Chapter 13). Thickening of capillary walls is caused by increased deposition of base- ment membrane-like material, as well as accumulation of immune complexes. Patients with this histologic change almost always have severe proteinuria with ove nephrotic syndrome (Chapter 13). * Advanced sclerosing lupus nephritis (class VI) is characterized by complete sclerosis of greater than 90% of glomeruli and corresponds to clinical end stage renal disease.
Focal sclerosis
Focal necrosis
Wire loop lesion
Diffused glomerulosclerosis
General anatomy