Where amyloid is deposited
The pathological protein affects various structures of the renal tissue. In the glomeruli, deposits are found in the mesangium, subepithelial space, and beneath the capillary endothelium, and over time they are capable of completely obliterating the glomeruli. Outside the glomeruli, amyloid masses are localized in the walls of blood vessels, along the basement membranes of the tubular epithelium, and in the interstitium.
Stages of disease development
The clinical course of the pathology goes through several successive stages:
- Latent stage.
- Proteinuric stage.
- Nephrotic stage.
- Azotemic stage.
The pathogenesis is based on severe proteinuria, which progresses to nephrotic syndrome, leads to glomerular destruction, and ends fatally from uremia.
Diagnostic methods
Histological examinations are used to confirm the diagnosis:
- Congo red staining: under conventional light microscopy, amyloid masses in the glomeruli and blood vessels acquire a characteristic brick-red or orange-red color.
- Polarization microscopy: examination of the same specimen reveals dichroism—a specific apple-green glow against a dark background, which serves as the gold standard for differentiating from other hyaline-like deposits.
Briefly: answers to topical questions
What do the kidneys look like macroscopically in the nephrotic stage of amyloidosis?
- Amyloidosis with nephrotic syndrome — Kidneys are dense; on the cut surface, they have a waxy (lardaceous) sheen.
How do the kidneys change macroscopically in the azotemic stage of amyloidosis?
- Amyloid contracted kidney — The final stage of renal amyloidosis involves the development of a contracted kidney form, leading to chronic renal failure.
What biochemical types of amyloid most commonly affect the kidneys?
- AA amyloid (AA-amyloid) — the type of amyloid in secondary (reactive) amyloidosis, which can develop, in particular, in rheumatoid arthritis.
What substances need to be differentiated from amyloid masses under light microscopy?
- Collagen (collagen) — a substance from which amyloid is differentiated using Congo red staining.
- Fibrin (fibrin) — a structure from which amyloid deposits must also be distinguished during histological diagnosis.
What is the pathogenesis of massive proteinuria development in amyloidosis?
- Impairment of filtration function (functio filtrationis) — Amyloid deposition in the glomeruli leads to impaired filtration function and severe proteinuria.
- Glomerular destruction (destructio glomerulorum) — The pathogenetic chain includes amyloid deposition, severe proteinuria, nephrotic syndrome, and glomerular destruction.
Congo red gives a color—under polarization, it strikes with green light!
Class and exam questions
Where exactly in the renal glomeruli are the first deposits of amyloid found?
Amyloid deposits are detected in the mesangium, beneath the capillary endothelium, and in the subepithelial space of the glomeruli, as well as in vessel walls and the interstitium.
Which method is considered the gold standard for diagnosing amyloidosis?
The combination of light microscopy with Congo red staining, in which the protein stains brick-red, and polarization microscopy, which yields an apple-green glow.
What are the main stages of the clinical course of the disease?
Latent, proteinuric, nephrotic, and azotemic stages are distinguished, which culminate in the development of renal failure and uremia.
What else to study on this topic
- Goodpasture syndrome and its morphological features
- Polyarteritis nodosa and Wegener's granulomatosis
- Idiopathic mixed cryoglobulinemia
- Multiple myeloma and renal involvement
- Light chain nephropathy and its manifestations
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