AMYLOIDOSIS DR. SANJIV KUMAR - PowerPoint Presentation

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AMYLOIDOSIS

DR. SANJIV KUMAR

ASSTT. PROFESSOR,

DEPTT. OF PATHOLOGY, BVC, PATNA

What is amyloidAmyloid (G.

Amylon

- STARCH) means starch-like. Amyloid is a pathologic glycoprotein deposited in the extracellular spaces and forms fibrils on polymerization.

HISTOLOGICAL CHARACTERISTICSOF AMYLOID

Amyloid

is specially stained with Congo Red. Under polarized light, green birefringence is noticed because of alignment of fibrils

.

β-pleated sheet configuration is seen in X-ray diffraction.

The P-component which is a

glycosa

-amino-glycan (GAG) facilitates polymerization of amyloid.

The

GAG makes the amyloid to stain with

iodine.

The amyloid is resistant to enzymatic digestion and progressively accumulate in tissues until the underlying disease process persists.

Types/Sources of amyloidAmyloid associated (AA): It occurs in chronic diseases and septic conditions. Precursor is serum amyloid associated protein (SAA).

Amyloid light-chain (AL): It is produced in

plasmacytoma

and the precursor is immunoglobulin light-chain.

AMYLOIDOSIS

Definition

It

is an immunological disorder in which homogeneous, translucent amyloid substance is deposited between capillary endothelium and adjacent cells.

Pathogenesis

The main event occurring in amyloidosis is the deposition of amyloid fibrils due to abnormality of protein processing.

The sources of amyloid may be acute phase proteins,

immunoglobulins

and endocrine secretes

.

The amyloid forms a β-pleated sheet despite their chemical heterogeneity. This makes the fibril resistant to digestion by macrophages and phagocytic cells and hence accumulates in tissues.The

amyloid, deposited around the blood vessels is more dangerous.

Pressure

atrophy of the adjacent cells and ischaemic anoxia results in degeneration and necrosis.

Due

to interference with gaseous exchange, supply of

nutritents

and removal of waste products and

stenotic

vessels, degeneration and necrosis of cells will occur amyloid precursor protein.

Types of amyloidosisPrimary amyloidosis

Secondary

amyloidosis

Primary amyloidosisIt

results from antigen-antibody reaction and deposition of its precipitates.

The

condition is not associated with any diseases e.g. repeated exposure to antigens as in antisera and antitoxin production in horses and B cell

dyscrasia

(

plasmacytoma

) in humans in which

immunoglobin

light chain deposition occurs.

The soluble immunoglobulin becomes insoluble with defective degradation.

Secondary amyloidosisThe condition may be associated with chronic diseases like tuberculosis, septic conditions and

neoplasia

.

This

occurs in two phases.

In

the initial

preamyloid

phase, there is accumulation of reticular cells and macrophages in the spleen and other lymphoid tissue with consequent rise in plasma SAAs and globulins

.

During the second phase, known as amyloid phase, PAS staining cells, amyloid deposition and fall in the SAAs level are found.

Grossly, the amyloid deposition may be diffuse or focal. The amyloid is deposited around the central artery of splenic follicles and it forms sheet like deposits which is referred as bacon

spleen

 and it may protrude resembling like a grain of sago known as 

sago spleen

.

The

organ is waxy in consistency and the cut surface is

grayish

.

Splenic

corpuscles become large,

gray

and translucent.

Liver

is enlarged with rounded edges, doughy in consistency, pits on pressure and ruptures easily because of its friable nature

.

In

renal amyloidosis, the organ is swollen, mottled, pale and yellow to orange in colour

Effects of amyloidosisHypovolumic

or haemorrhagic shock may occur following hepatic rupture

.

Hepatocellular

atrophy occurs from pressure and nutritional deficiency

.

In

renal amyloidosis,

interfere

with glomerular filtration.

The

enlargement and ischaemic anoxia leads to tubular epithelial degeneration and necrosis, marked proteinuria,

nephrotic

syndrome,

uremia

and death

In pancreatic amyloidosis,

leads

to islet cell destruction and development of Diabetes mellitus.

Blindness

may be encountered in horses in with

conjuctival

amyloid deposition.