Abstract
BackgroundFocal segmental glomerulosclerosis (FSGS) lesions have often been discussed as a negative predictor in idopathic membranous nephropathy (MN). The mechanism of the development of FSGS lesion in MN is still uncertain.MethodsFrom 250 cases of MN, 26 cases contained FSGS lesion. We compared the clinicopathological characteristics between MN cases with FSGS lesion [MN-FSGS(+)] and MN without FSGS lesion [MN-FSGS(−)], matched for gender, age, stage of MN.ResultsThe glomerular filtration rate (eGFR) was significantly lower in MN-FSGS(+) cases compared to MN-FSGS(−), although nephrotic syndrome, hematuria, and systolic blood pressure levels were not significantly different between the two groups. Pathologically, glomeruli in MN-FSGS(+) cases showed narrowing and loss of glomerular capillaries with separating from GBM or disappearance of CD34+ endothelial cells, and accumulation of extracellular matrix (ECM) in capillary walls, indicating the development of glomerular capillary injury. These findings of endothelial injury were seen even in MN-FSGS(−) cases, but they were more prominent in MN-FSGS(+) than MN-FSGS(−) by computer assessed morphometric analysis. In MN-FSGS(+) cases, 44 out of 534 glomeruli (8.2%) contained FSGS lesions (n = 31, NOS lesion; n = 13, perihilar lesion). Significant thickness of GBM with ECM accumulation was evident in MN-FSGS(+) cases. Podocyte injury with effacement of foot processes was also noted, but the expression of VEGF on podocytes was not different between the two groups, which suggests that the significant thickness of capillary walls may influence the function of VEGF from podocyte resulting in the glomerular capillary injury that contribute to the development of FSGS lesion in MN.ConclusionGlomerular capillary injury was seen in all MN cases. Furthermore, the prominent injuries of glomerular capillaries may be associated with the deterioration of eGFR and the formation of FSGS lesions in MN.
Highlights
Idiopathic membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome in adults [1,2]
The glomerular filtration rate was significantly lower in MN-Focal segmental glomerulosclerosis (FSGS)(+) cases compared to MN-FSGS(−), nephrotic syndrome, hematuria, and systolic blood pressure levels were not significantly different between the two groups
Significant thickness of glomerular basement membrane (GBM) with extracellular matrix (ECM) accumulation was evident in MN-FSGS(+) cases
Summary
Idiopathic membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome in adults [1,2]. The course of MN is quite variable, with an estimated one third of patients undergoing spontaneous remission of proteinuria, another third with persistent proteinuria, and the remaining third progressing to end-stage renal failure [2,3]. Because of such variable natural history of MN, the identification of parameters that predict the prognosis of MN is important in order to select appropriate treatment, conservative or immunosuppressive therapy. Focal segmental glomerulosclerosis (FSGS) lesions have often been discussed as a negative predictor in idopathic membranous nephropathy (MN). The mechanism of the development of FSGS lesion in MN is still uncertain
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