This document discusses amyloidosis, a condition caused by extracellular deposition of fibrillar proteins that can damage tissues. There are two main types - AL amyloidosis associated with plasma cell disorders and AA amyloidosis linked to inflammation. Common sites of deposition include kidneys, liver, spleen, and heart. Amyloid is identified on histology as an extracellular eosinophilic deposit that stains red with Congo red dye under polarized light. The deposits can obstruct organs over time and cause nonspecific symptoms. Biopsy with Congo red staining is important for diagnosis.

1. AMYLOIDOSIS
Dr. Anshita Dubey

2. • Amyloidosis is a condition associated with a number
of inherited and inflammatory disorders in which
extracellular deposits of fibrillar proteins are
responsible for tissue damage and functional
compromise

4. fibrillar deposits bind proteoglycans and glycosaminoglycans
abundant charged sugar groups in these adsorbed proteins gives deposit staining
resemble starch (amylose).
deposits are unrelated to starch.

5. • nonbranching fibrils, 7.5 to 10 nm in diameter, each formed of β-sheet
polypeptide chains that are wound together
misfolded proteins
degraded intracellularly in proteasomes extracellularly by
macrophages
accumulate outside the cells

6. • two general categories:
(1) normal proteins that have an inherent tendency to fold improperly,
associate to form fibrils when they are produced in increased amounts
(2) mutant proteins that are prone to misfolding and subsequent
aggregation

7. • 3 most common amyloid :
AL Amyloid : plasma cells
made up of complete immunoglobulin light chains, the amino-
terminal fragments of light chains, or both.
a/w monoclonal B cell proliferation
Defective degradation
particular light chains are resistant to complete proteolysis

9. • The AA fibril :
SAA AA
(liver)
IL-6 and IL-1 (inflammation)
SAA monocyte-derived enzymes soluble end products
a genetically determined structural abnormality in the SAA molecule itself renders
it resistant to degradation by macrophages

10. • Aβ amyloid - cerebral lesions of Alzheimer disease.
amyloid precursor protein (APP) -------- Aβ
other proteins : Transthyretin (TTR)
normal protein binds and transports thyroxine and retinol
mutations - prone to misfolding and aggregation, and resistant to proteolysis.
Familial amyloid polyneuropathies
heart of aged persons (senile systemic amyloidosis) - structurally normal, but
accumulates at high concentrations.

11. • β2-Microglobulin - component of MHC class I molecules and a normal serum
protein,
• fibril subunit (Aβ2m) in amyloidosis
long-term hemodialysis
retained in the circulation because it is not
efficiently filtered through dialysis
membranes.

13. On clinical grounds, systemic
primary amyloidosis ------ associated with a monoclonal plasma cell proliferation
secondary amyloidosis ------ complication of an underlying chronic inflammatory or
tissue destructive process

14. • Primary - heart, gastrointestinal tract, respiratory tract, peripheral nerves, skin,
and tongue
• Secondary - kidneys, liver, and spleen
• Gross - the organ is enlarged and the tissue typically appears gray with a waxy,
firm consistency

15. On histologic examination, the amyloid deposition is always extracellular
begins between cells,
(often closely adjacent to basement membranes)
As the amyloid accumulates, it encroaches on the cells ---destroy
In the AL form ------ perivascular and vascular localizations are common.

16. STAINS

18. CONGO RED
• FLUORESCENT DYE; NOT SPECIFIC FOR AMYLOID
Staining – hydrogen bonding between congo red and B pleated sheet in a highly
oriented linear and parallel manner.
If the spatial configuration is altered-----------> reaction fails
Postive birefringence- parallel arrangement of dye molecules

19. • Interpretations :
AMYLOID – SALMON RED
NUCLEI – BLUE
UNDER POLARIZED LIGHT MICROSCOPE:
AMYLOID : APPLE GREEN
COLLAGEN : YELLOW RED

20. Principle : di azo dye which attaches itself parallel to the fibrils of amyloid and
forms non polar hydrogen bonds- shows green birefringence of congo red stained
amyloid under polarised light.

21. Lugols iodine

22. • Lugol’s Iodine - : Iodine 5% and KI 10%
Iodine is not soluble in water, therefore KI
I2 + I- ------------ I3-
This makes a linear triiodide ion complex which is soluble. The triiodide ion slips
into the coil of the starch causing an intense blue-black color

23. Metachromatic dyes
Methyl/ crystal violet Toulidine blue
• The dye reacts with the tissues to produce a color different from that of the
original dye and from the rest of the tissue
• It is attributed to stacking of dye cations at the sites of high density of
anionic groups in the tissue. Stacking shortens the wavelength of
maximum absorption
• Substances that can be stained in this way are called chromotropes.

24. METHYL/ CRYSTAL VIOLET
• Metachromatic stains
negatively charged groups on the tissue + cationic dyes
polymerization
original colour of the dye changes to another colour
Amyloid – purple red on a green background

25. TOLUIDINE BLUE
Thiazine metachromatic dye with high
affinity for acidic tissue components.
Amyloid stains – weak basophilic

26. THIOFLAVIN T (fluorescent dye)
• Thioflavin T is a benzothiazole salt
• Dye interacts with the quaternary structure of B pleated sheet rather than with
protein moieties, so binding is not dependent on any amino acid sequence.
Acidic pH increases the selectivity by favouring the fluorochrome fraction
binding to amyloid while depressing non amyloid fluorochrome staining.
• In vivo and in vitro

27. ALCIAN BLUE
• PRINCIPLE : polyvalent basic dye
Forms salt linkages with acid groups of
sulphated and carboxylated acid
mucoploysaccharides
• Amyloid deposits - Shades of green
• Fibrin, muscle, cytoplasm – Yellow
• Collagen, stroma - Red
• Nuclei - Black

28. PAS stain
Periodic acid oxidises the 1:2 glycol groups in the tissue to dialdehydes.
Amyloid – light pink

29. HAEMATOXYLIN & EOSIN STAIN
• HEMALUM (ALUMINIUM IONS & OXIDISED HAEMATOXYLIN) ---- NUCLEI
• COUNTERSTAIN WITH AQUEOUS OR ALCOHOLIC SOLUTION OF EOSIN Y
Amyloid - eosinophilic

30. IHC

31. P COMPONENT
• Makes 10% of amyloid weight
• Found on all amyloid fibrils except alzheimers senile plaques
• Stabilizes fibril amyloid protein and decreases their clearance
• Plays role in some of the special stains

32. KIDNEY
most common and most serious feature of the disease
Grossly – unchanged / may be abnormally large, pale, gray, and firm;
in long-standing cases - may be reduced in size.
Microscopically - the amyloid deposits are found in the
glomeruli interstitial peritubular tissue & in the walls of the
blood vessels.

33. • The glomerulus - focal deposits within the mesangial matrix and diffuse or
nodular thickenings of the basement membranes of the capillary loops.
the deposition encroaches on the capillary lumina - total obliteration of the
vascular tuft
The interstitial peritubular deposits
amorphous pink casts within the tubular
lumens
walls of blood vessels - marked vascular
narrowing.

34. SPLEEN
• moderate or even marked enlargement (200 to 800 gm).
• 2 PATTERNS –
deposits limited to the splenic follicles, producing tapioca-like granules on gross
examination (“sago spleen”)

35. involve the splenic sinuses, eventually extending to the splenic pulp, with
formation of large, sheetlike deposits (“lardaceous spleen”)
In both patterns, the spleen is firm in consistency.

36. LIVER
GROSS - massive enlargement (9000 gm). Pale, grayish, and waxy on both the
external surface and the cut section.
MICRO - amyloid deposits first appear in the space of Disse
adjacent hepatic parenchyma and sinusoids

37. HEART
• systemic involvement - AL form.
• The isolated form (senile amyloidosis) – older persons.
minimal to moderate cardiac enlargement
gray-pink, dewdrop-like subendocardial elevations(atrial chambers)
histologic examination - throughout the myocardium
myocardial fibers
pressure atrophy

38. Clinical Course & Diagnosis
• Nonspecific complaints - weakness, fatigue, and weight loss
• Later - renal disease, hepatomegaly, splenomegaly, or cardiac abnormalities
• Biopsy and subsequent Congo red staining is the most important tool
• renal biopsy - urinary abnormalities
Rectal and gingival biopsy specimens - generalized amyloidosis.
Examination of abdominal fat aspirates stained with Congo red - simple, low-risk
method.
Bone marrow examination - plasmacytosis

39. THANK YOU