Amyloid

Question 1

What is amyloid?

Answer 1

a class of insoluble abnormal protein deposits in tissue

Question 2

What is amyloidosis?

Answer 2

disease condition where amyloid is deposited locally or systemically

Question 3

Name the 2 classifications of amyloidosis

Answer 3

1. systemic - involves more than one organ

2. localized - restricted to a single organ or tissue

Question 4

How is amyloid identified grossly?

Answer 4

iodine-sulfuric acid method to stain amyloid deposits in tissue at necropsy

Question 5

How is amyloid identified microscopically?

Answer 5

H&E stain
Congo red stain
Thioflavin S or T

Question 6

What is the structure/composition of amyloid?

Answer 6

• fibrils

- protein secondary structure beta-pleated sheets

Question 7

What is the significance of replacement of functional tissue with amyloid?

Answer 7

• physical compression of normal tissues resulting in atrophy
• disruption of normal structures and impaired function

Question 8

Nomenclature of amyloid

Answer 8

“A” (for amyloid) followed by abbreviation for protein precursor (ex: AA, AL, etc.)

Question 9

What is the significance of cytotoxic amyloid oligomers and/or fibrils?

Answer 9

• induce cell stress responses and apoptosis

Question 10

Pathogenesis of amyloidosis

Answer 10

1. increased production of precursor protein
2. mutation in precursor protein resulting in more amyloidogenic form
3. abnormal processing of precursor protein to form amyloidogenic polypeptides

Question 11

Characteristics of AA (secondary/reactive) amyloidosis

Answer 11

• most serious systemic form in mammals and birds
• occurs secondary to recurrent or chronic disease
• increased hepatic synthesis of SAA
• macrophage degradation of SAA to amyloidogenic fragment

Question 12

Clinical signs of systemic AA amyloidosis

Answer 12

• renal glomerulus problems
• marked proteinuria and renal failure
• hepatic failure may develop with severe liver involvement

Question 13

Which gene mutation has recently been linked to Shar Pei AA amyloidosis?

Answer 13

HAS2 gene

Question 14

What is the second form of canine amyloidosis?

Answer 14

• pulmonary vascular amyloid (most common systemic form)
• found in large proportion of aged dogs
• derived from apolipoprotein A1

Question 15

what is the third form of canine amyloidosis?

Answer 15

• beta-protein derived (Alzheimer’s-like) cerebral amyloid

- associated with cognitive dysfunction

Question 16

What is the first form of feline amyloidosis?

Answer 16

• systemic AA amyloidosis
• uncommon except in Abyssinian, Siamese, and Oriental short hair cats
• can cause hepatic failure and rupture

Question 17

What is the second form of feline amyloidosis?

Answer 17

• islet amyloidosis

- long-standing insulin resistance results in increased production of IAPP

Question 18

What form of diabetic cats have islet amyloidosis?

Answer 18

type 2 diabetics

Question 19

What is the form of bovine amyloidosis?

Answer 19

• systemic AA amyloidosis
• involves renal (proteinuria) and/or GI tract (severe diarrhea)
• often associated with food abscesses and necrotizing pododermatitis

Question 20

What are the two forms of equine amyloidosis?

Answer 20

• systemic AA amyloidosis (liver or GI involvement)

- localized AL form (nodular skin form or multinodular nasopharyngeal form)

Question 21

Systemic AA amyloidosis can occur in which exotic wildlife species?

Answer 21

cheetahs
gazelles
black-footed cats
black-footed ferrets

Question 22

What is the form of avian amyloidosis?

Answer 22

systemic AA amyloidosis (high incidence in waterfowl)

Question 23

Features of AA amyloidosis in spleen

Answer 23

• multifocal white spots (involvement of white pulp)

- generalized enlargement of spleen (involvement of red pulp)

Question 24

Features of AA amyloidosis in liver

Answer 24

hepatomegaly
pale/yellow
heavy
friable
atrophy of hepatic cords

Question 25

Features of AA amyloidosis in kidneys

Answer 25

• mottled pale tan and red with prominent glomeruli
• glomerular deposits in mesangium and within the capillary walls
• obliteration of glomerulus