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, eventually capable of completely obliterating the glomeruli. Outside the glomeruli, amyloid masses localize in the walls of blood vessels, along the tubular epithelial basement membranes, 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 driven by severe proteinuria that progresses to nephrotic syndrome, leads to glomerular destruction, and culminates in death from uremia.
Diagnostic Methods
Histological studies are used to confirm the diagnosis:
- Congo red staining: Under a standard light microscope, amyloid masses in glomeruli and vessels acquire a characteristic brick-red or orange-red color.
- Polarization microscopy: Examination of the same slide reveals dichroism — a specific apple-green birefringence against a dark background, serving as the gold standard for differentiation from other hyaline-like deposits.