Accumulations & Deposits

Intracellular Accumulations

buildup of substances that cells cannot immediately use or eliminate

Three categories of intracellular accumulations:

1.) normal cellular component accumulated in excess

2.) abnormal substance

3.) pigments

normal cellular component accumulated in excess

water, lipids, glycogen, or carbohydrates that are accumulated in excess in a cell

abnormal substance accumulations

exogenous (mineral, infectious agent) or endogenous (abnormal synthesis during metabolism)

pigment accumulations

substances located in the cytoplasm or nucleus

two fates of pigment accumulations

1.) permanent

2.) transient (temporary)

Four mechanisms of intracellular accumulations

1.) abnormal metabolism

2.) defect in protein folding + transport

3.) lack of enzyme

4.) ingestion of indigestible materials

intracellular accumulation mechanism: abnormal metabolism

Normal endogenous substance is produced at a normal or increased rate, but the rate of metabolism is inadequate to remove it from the cell

intracellular accumulation mechanism: defect in protein folding + transport

Abnormal endogenous substance accumulates due to a defect in protein folding or transport; abnormal proteins accumulate

intracellular accumulation mechanism: lack of enzyme

Normal endogenous substance accumulates due to a defect in an enzyme that is normally required for metabolism

intracellular accumulation mechanism: ingestion of indigestible materials

Abnormal exogenous substance in ingested by the cell and accumulates since the cell cannot degrade/transport it out

Five examples of intracellular accumulations

1.) Hyaline

2.) Inclusion bodies

3.) Amyloid

4.) Gout

5.) Pathologic calcification

Hyaline accumulations

protein that is deposited in tissues

Hyaline appearance using H&E stain

-homogenous

-eosinophilic (pink)

-amorphous

-glassy

*small bright pink dots in image

Two scenarios that would result in hyaline accumulations

1.) resorption of hyaline droplets due to proteinuria (such as during kidney disease)

2.) russel bodies in plasma cells

What stain can be used to better visualize hyaline droplet accumulations?

periodic acid-schiff (PAS)

*looks like dark pink dots

Pathogenesis of hyaline droplet accumulations due to kidney disease

glomerular damage --> leads to proteinuria --> protein is taken up by proximal tubular epithelial cells, forming the hyaline protein droplets

russel bodies

hyaline bodies present in the cytoplasm of some plasma cells (Mott cells)

Appearance of russel bodies

-large

-eosinophilic

-homogenous

-amorphous

What are russel bodies made of?

accumulated immunoglobulin within plasma cells

What disease is associated with russel bodies?

feline plasma cell pododermatitis

feline plasma cell pododermatitis

disease where the dermis and some of the underlying adipose tissue is infiltrated with plasma cells, some of which contain hyaline accumulations

Inclusion bodies

nuclear and cytoplasmic aggregates of material

Two types of inclusion bodies:

1.) crystalline protein inclusion bodies

2.) viral inclusion bodies

crystalline protein inclusion bodies

found in normal hepatocytes and renal tubular epithelium

crystalline protein inclusion bodies are especially found in what age/species?

old dogs

crystalline protein inclusion bodies appearance

-large

-eosinophilic

-rhomboid

viral inclusion bodies

Nuclear or cytoplasmic aggregates made of proteins created by a virus

Amyloid accumulations

Pathologic extracellular, insoluble, proteinaceous (hyaline) substance resistant to proteolysis and deposited between cells

Amyloid fybrils

abnormally folded proteins in a β- sheet confirmation; make up amyloid accumulations

What is the pathologic significance of amyloid accumulations?

amyloid accumulations mechanically interfere with the cell (by sandwiching in between cells), and thus interfere with their function

Two consequences of amyloid accumulations

1.) organ failure

2.) protein losing "organ-opathy"

What organs commonly fail due to amyloid accumulations?

kidney and liver

What organs commonly have protein losing "organ-opathies" due to amyloid accumulations?

kidney and intestines

Two types of amyloid accumulations:

1.) reactive systemic- Amyloid associated (AA)

2.) primary amyloid- Amyloid light chain (AL)

reactive systemic- Amyloid associated (AA)

amyloid accumulation composed of amyloid associated protein (AA); secondary to chronic antigen stimulation (such as due to chronic infection, neoplasia)

reactive systemic- Amyloid associated (AA) accumulations are most common in _________

animals

What canine species are reactive systemic- Amyloid associated (AA) accumulations hereditary in?

Shar peis

What feline species are reactive systemic- Amyloid associated (AA) accumulations hereditary in?

Abyssinian cats

What is the precursor protein of reactive systemic- Amyloid associated (AA) accumulations?

serum amyloid associated protein (SAA)

serum amyloid associated protein (SAA)

acute phase protein, produced during inflammation, part of the acute phase response

primary amyloid- Amyloid light chain (AL)

amyloid accumulation composed of amyloid light chain protein (AL); found in plasma cell tumors and myelomas

amyloid light chain protein (AL)

Derived from abnormal plasma cells secreting immunoglobulin light chain fragments into circulation

primary amyloid- Amyloid light chain (AL) accumulations are most common in _________

humans

Amyloid accumulations pathogenesis (4)

1.) Precursor proteins (SAA or light chains) are in circulation

2.) partial degradation of precursor proteins occurs, causing them to be misfolded

3.) misfolded protein is deposited in the tissues, forming aggregates

4.) misfolded protein aggregates form amyloid fibrils that displace and compress cells

Five common locations of amyloid accumulation in all species:

1.) kidney

2.) liver (space of disse)

3.) spleen (germinal centers)

4.) lymph nodes (germinal centers)

5.) adrenal cortex

Where are amyloid accumulations located specific to horses?

skin and nasal septum and turbinates

Where are amyloid accumulations located specific to cats?

pancreatic islets of Langerhans

Gross morphological features of amyloid accumulations

-pale

-tan to yellow

-waxy

-swollen and enlarged

What special stain is used to grossly identify amyloid accumulations?

Lugol's iodine solution; form small black dots

Microscopic features of amyloid accumulations

-eosinophilic

-amorphous

-looks like "cotton candy"

What special stain is used to microscopically identify amyloid accumulations?

Congo red; stains orange to red

Under fluorescence, what will amyloid accumulations look like while stained with congo red?

apple green color

Gout accumulations

deposition of sodium urate crystals or urates in the tissues

Two locations of gout accumulations

1.) viscera

2.) joints

Three species affected by gout accumulations

1.) humans

2.) birds

3.) reptiles

Why are humans, birds, and reptiles affected by gout accumulations?

they lack the enzyme uricase

uricase

aka urate oxidase; enzyme that catalyzes the oxidation of uric acid to allantoin (a substance that is more easily secreted)

Examples of things that can lead to gout accumulations

-dehydration

-high protein diets

-renal failure

**anything that disrupts excretion of uric acid!

Two reasons gout accumulations mainly occur:

1.) impaired excretion of uric acid by the kidneys (such as due to dehydration, severe renal disease, nephrotoxic drugs, etc)

2.) overproduction of uric acid (such as due to excessive protein in the diet, inherited enzyme defects)

Pathogenesis of gout accumulations

1.) species lacks the enzyme uricase

2.) leads to elevation of plasma uric acid concentration

3.) causes precipitation of urate crystals on either visceral or articular surfaces

4.) leads to chronic inflammation (usually in articular form)

In birds and reptiles, is the articular or visceral form of gout accumulations more common?

visceral form

Two organs classically affected by visceral gout accumulations

1.) heart (pericardium)

2.) kidneys

Gross appearance of gout accumulations

chalky white nodules

Microscopic appearance of gout accumulations

urate crystals surrounded by inflammatory response (macrophages, neutrophils)

Pathologic calcification accumulations

calcium deposits that occur in the soft tissues rather than in bones

Two types of pathologic calcification accumulations

1.) dystrophic calcification

2.) metastatic calcification

dystrophic calcification accumulations

calcium deposits on visibly diseased or necrotic tissue

What causes dystrophic calcification accumulations?

dead cells release phosphates which combine with calcium and form depositions

metastatic calcification accumulations

calcium deposits on visibly normal tissue

metastatic calcification accumulations are indicative of...

other diseases going on in the body; typically systemic metabolic diseases that lead to elevated serum calcium levels

Two causes of elevated serum calcium levels that lead to metastatic calcification accumulations:

1.) hyperparathyroidism (primary cause, such as PTH related protein secreting tumors)

2.) hypercalcemia (secondary to vitamin D toxicity, renal failure, etc)

Dystrophic vs metastatic calcification:

tissue type

Dystrophic calcification: necrotic tissue

metastatic calcification: normal tissue

Dystrophic vs metastatic calcification:

serum calcium levels

Dystrophic calcification: normal serum calcium

metastatic calcification: hypercalcemia

Gross appearance of pathologic calcification accumulations

gritty, hard white appearance

Microscopic appearance of pathologic calcification accumulations

calcium deposits are purple/blue with H&E stain

What special stain is used to visualize pathologic calcification accumulations?

von Kosa stain; stain black

Two pigments:

1.) cyanosis

2.) hemosiderin

cyanosis

blue color due to deoxygenated hemoglobin

What condition is cyanosis common in?

saddle thrombus in cats; blood clot prevents blood flow to rear legs and leads to blue color on paw pads

hemosiderin

iron storage pigment; golden brown color

What organ is hemosiderin mostly stored in?

spleen

What could cause increased amounts of hemosiderin?

-breakdown of erythrocytes

-hemorrhage

-congestion (slow blood flow)

-hemolysis

Case 1:

-3.5-year-old, neutered male, SharPei

-Recurrent episodes of fever of unknown origin (ie, 103°F-107°F) , with concurrent swollen, painful hocks, swelling of the muzzle, abdominal pain, diarrhea, and anorexia

Based on the histopathology, which histochemical stain would you request?

A. Von Kossa

B. Lugol's Iodine

C.Congo Red

D. Oil Red O

C. Congo Red

-amorphous

-light pink material

-looks like "cotton candy" in space of disse of liver and glomerulus in the liver,

-characteristic of amyloidosis

Case 1:

What are the structures being highlighted by this stain?

A. Renalmedulla

B. Islets

C. Spaceof Disse

D. Glomeruli

D. Glomeruli

Case 1:

What type of Amyloidosis is this?

A. Immunoglobulin‐associated (primary, AL)

B. Reactive (secondary, AA)

C. Apolipoprotein AI-derived amyloidosis

D. Islet amyloid polypeptide-derived amyloidosis

B. Reactive (secondary, AA)

-secondary to chronic antigen stimulation (such as due to chronic infection, neoplasia)

-breed disposition (Shar pei)

Based on the histopathology of amyloid accumulations in the picture, what is the likely species of the patient?

A. Horse

B. Dog

C. Cow

D. Cat

D. Cat

*islets of Langerhaans specific to cats

Case 2:

-8 day-old female alpaca cria presented with an abrupt onset of recumbency and illness.

-Clinically she was lethargic, febrile and had an elevated cardiac and respiratory rate.

-It was later revealed that she was being fed a powdered goat colostrum supplement

Gross pathology:

-Bilaterally kidneys were paler than normal

-Multifocal, gritty, hard foci on cut surface

Histopathology:

-in both kidneys, glomeruli are diffusely replaced by hard, readily fractured, intensely basophilic granular to homogeneous material consistent with mineral/calcification

Lab results:

Calcium highly elevated (13.1 compared to RI of 2-2.6)

Which type of calcification is this?

A. Metastatic

B.Dystrophic

A. Metastatic

-for metastatic, serum calcium will be high; for dystrophic, serum calcium will be normal

What is this?

A. Hyaline

B. Mott cells

C. Amyloid

D. Calcification

A. Hyaline

-homogenous

-eosinophilic (pink)

-amorphous

-glassy

*small bright pink dots in image to the right

What is the cause of this lesion?

A. Deposition of insoluble masses of glycoprotein fibrils arranged in β-pleated sheets

B. Deposition of insoluble minerals (carbonate and phosphate salts of Ca+,Mg+, and K+)

C. Deposition of an amorphous, eosinophilic protein material

D. Deposition of urate crystals on articular/synovial surfaces of joints and/or serous surfaces of viscera

D. Deposition of urate crystals on articular/synovial surfaces of joints and/or serous surfaces of viscera

Gout!!

-chalky white

-changes from gritty to pasty depending

**A is amyloid

**C is very nonspecific, could to apply to anything

**B is good differential but due to location of this deposition (serous surface of viscera) more likely to be D

Which of the following is a cause of metastatic calcification?

A Renal disease

B Vitamin D toxicity

C Paraneoplastic syndrome

D All of the above

D All of the above

What does the histochemical stain Congo Red detect?

A Lipid

B Glycogen

C Amyloid

D Mineral

C Amyloid