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[Clinical pathology of the glomerulus--from phenomenon to entity. The membranous lesion]
Abstract:
Characteristics of the membranous lesion are usually the capillary wall thickening in morphology and the clinical manifestation of a nephrotic syndrome. As entities of such a lesion the following types of glomerulonephritis (GN) could be considered: (peri-) membranous GN, garland type of postinfectious GN, and membranoproliferative (MP) GN. The morphological, especially the electronmicroscopical observations relative to separate immune deposit locations in the capillary wall--subendothelial, intramembranous, subepithelial--are the basis to differentiate the diseases as entities. The characteristic finding of the (peri-) membranous GN is the presence of subepithelial immune deposits along the capillary walls, which are separated by "spikes" and later on are incorporated into the basement membrane, while some of the deposits became rarefied; on the other hand, new subepithelial deposits can be observed when the disease of the most common idiopathic form starts again after a period of remission.--The deposits of the garland type of the postinfectious GN--the disease is more often a chronic progressive process than the other types of postinfectious GN--are in a subepithelial location. In contrast to the former the deposits vary in size and number and only some capillary walls are affected.--In type I of the MPGN the immune deposits are located mainly in a subendothelial position, often together with a mesangial interposition in such a manner, that the capillary wall has the appearance of "double contour" histologically. The most striking change of type II is the presence of dense deposits in the lamina densa of the capillary basement membrane ("dense deposit GN"). In type III of MPGN the deposits are located in all three positions of the capillary wall--subendothelial, intramembranous, subepithelial--and the lamina densa is markedly disrupted (little or no affinity for silver in thin sections after silver impregnation). Concerning the entity of the 3 types of MPGN, the depression of serum complement and the complement activating C3-nephritis factor are persistent features of type II, while these findings are obvious only in 50% of type I and III-diseases.
Insights
This study differentiates glomerulonephritis (GN) types by examining immune deposit locations within capillary walls. Electron microscopy is key to distinguishing membranous GN, postinfectious GN, and membranoproliferative GN subtypes.
Area of Science:
- Nephrology
- Pathology
- Immunology
Context:
- Membranous lesions in kidney glomeruli often present as capillary wall thickening and nephrotic syndrome.
- Distinguishing between (peri-)membranous GN, postinfectious GN (garland type), and membranoproliferative (MP) GN is crucial for diagnosis.
- Immune deposit location within the glomerular capillary wall (subendothelial, intramembranous, subepithelial) is a primary diagnostic criterion.
Purpose:
- To elucidate the distinct morphological characteristics of various glomerulonephritis (GN) entities based on immune deposit localization.
- To provide electron microscopic criteria for differentiating (peri-)membranous GN, postinfectious GN, and the three types of MPGN.
- To correlate specific deposit patterns with clinical and serological findings, such as complement depression.
Summary:
- (Peri-)membranous GN shows subepithelial deposits, often with "spikes."
- Garland type postinfectious GN has subepithelial deposits that vary in size and affect some capillary walls.
- MPGN Type I features subendothelial deposits with mesangial interposition ("double contour"); Type II has dense deposits in the lamina densa; Type III exhibits deposits in all three locations with lamina densa disruption. Type II MPGN is associated with persistent C3-nephritis factor and complement depression.
Impact:
- Provides a framework for accurate diagnosis of glomerular diseases based on detailed ultrastructural analysis.
- Facilitates understanding of the pathogenesis of different glomerulonephritis types.
- Aids in clinical decision-making and prognosis by clarifying disease entities.