| Familial Amyloidosis
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characterized by deposition of amyloid AA, mainly in the medullary interstitium, e.g. Shar Pei dogs
and Abyssinian cats.
Grossly:
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kidneys with amyloidosis are enlarged, pale and yellow and have a granular surface;
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amyloid stains black when Lugol's iodine is applied to fresh tissue → with glomerular amyloidosis,
one can see numerous black dots which represent glomeruli containing deposits of amyloid protein.
Microscopically:
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deposits of pink amorphous material in glomeruli (most species) or in medullary interstitium (cats in
particular);
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Congo red stain (with polarized light) is used to confirm amyloidosis;
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glomerular form
➝
impairs glomerular filtration, causing protein-losing glomerulopathy
(proteinuria);
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medullary form
➝
impairs medullary function;
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in chronic cases, the physical presence of amyloid causes ischemia and pressure atrophy of
nephrons, and resultant scarring.
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