Amyloidosis

Dr Niranthi Perera

Learning outcomes

You should be able to1. list the different methods by which

Amyloid is identified in the laboratory2. describe the different types of clinical

situations where Amyloidosis occurs3. work out the effects of Amyloidosis in

different tissues of the body.

Amyloid• A variety of fibrillar proteins with a beta-pleated structure• does not have a constant chemical composition• is insoluble and relatively resistant to proteolytic

digestion• Therefore accumulates extra-cellularly in the

walls of blood vessels in tissues and interferes with their function, causing gradual destruction of vital organs

Physico-chemical features of Amyloid are due to the beta pleated structure

• When iodine is added to the surface of a fresh organ containing amyloid, a brown colour is produced

• Amyloid stains a homogenous pink with the commonly used Haemotoxylin and eosin stains

• With a Congo red stain it appears red, and shows an apple-green birefrigence under polarised light

Light microscopy

Congo red

Congo red

• With methyl violet, amyloid shows metachromasia

• Shows immuno-fluoroscence with the Thioflavine stain

• On electron microscopy, amyloid appears as non-branching fibrils

• Amyloid may be stained immuno-histochemically using antibodies specific to the various sub-types of fibrils

Physico-chemical features of Amyloid – ctd

Fluorescence

Electron microscopy

Chemical composition of Amyloid

1. Amyloid of Immunoglobulin originAL Amyloid (Amyloid light chain)

Produced by neoplastic plasma cells in multiple myeloma

Produced by neoplastic B lymphocytes in lymphoma

Chemical composition - ctd

2. Amyloid-associated protein(AA protein)serum amyloid-associated protein produced bythe liver AA protein is typically deposited in the setting of chronic inflammation

3. Other amyloid proteins

ATTR – transthyretin protein – Hereditary Amyloidosis and Senile Amyloidosis

Aβ2m – β2 microglobulin – chronic renal failure

Aβ – Amyloid precursor protein – Alzheimer disease

Chemical composition - ctd

Pathogenesis of Amyloid

Stimulus

Soluble precursor

Insoluble fibrils

chronic inflammation

Macrophages secrete IL I and 6

Liver cells secrete SAA protein

AA protein

Pathogenesis of AA protein

Pathogenesis of AL protein

unknown stimulus

Monoclonal B lymphocyte proliferation

Plasma cellssecrete Immunoglobulin light chains

AL protein

Why is it necessary?Because a given biochemical form of amyloid may be associated with deposition of Amyloid in diverse clinical settings

Amyloidosis

Systemic Localisedinvolves several involves a organ systems single organ

Clinical classification of Amyloid

Primary Amyloidosis ALSystemic pattern immunocyte dyscrasias

Secondary Amyloidosis AA in chronic inflammation

Localised Heredo-familial

Clinical classification of Amyloid

Clinical classification of Amyloid

Based on the type of protein and where it is distributed

A. Systemic AmyloidosisB. Localised AmyloidosisC. Amyloid in neoplasms D. Heredo-familial amyloidosisE. Senile Amyloidosis

Pattern of distribution

1. Primary pattern of distribitionHeart, GIT, tongue, skin, nerves

2. Secondary pattern of distributionliver, spleen, kidney, adrenals, GIT, skin

A. Primary Amyloidosis

- ususally of systemic distribution of AL type- increased number of plasma cells in bone

marrow produce immunoglobulin light chains

- AL amyloid derived from immunoglobulin light chains- seen in plasma cell myeloma and

lymphoma

B. Reactive systemic Amyloidosis

- has a systemic pattern of distribution- liver, spleen, kidney, adrenals, GIT, skin- prolonged cell injury (chronic inflammation) in infectious and non-infectious disease- eg Tuberculosis, leprosy, chronic pyelonephritis,

chronic osteomyelitis, inflammatory bowel disease- AA protein derived from plasma alpha1globulin

C. Amyloid in neoplasms(a type of localised Amyloidosis)

• Amyloid is seen in many endocrine neoplasmseg;- medullary carcinoma of thyroid

pancreatic islet-cell adenomas

• Protein is AE derived from peptide precursors

D. Heredo-familial Amyloidosis

• Familial Mediterranean fever is transmitted as an Autosomal Recessive inheritance in Jews, with fever and serosal and joint inflammation AA amyloid

• Familial Amyloidotic polyneuropathy is an Autosomal Dominant inn Portugal, Japan,

amyloid is deposited in peripheral and autonomic nerves

ATTR amyloid

E. Senile Amyloidosis

• Found in elderly• Systemic deposition of Amyloid in the

heart, pancreas and spleen

Heart – arrhythmias, restrictive cardiomyopathy

Transthyretin amyloid protein

F. Localised Amyloidosis

• Nodular tumour-like masses in tongue, bladder, lung, larynx, or skin (amyloid tumours)

• In Alzheimers disease, special amyloid plaques are deposited in the brain extra-cellularly

Effects of Amyloid deposition on tissues

• Site is in interstitial tissue, in relation to the basement mamebrane of cells and small blood vessels

• Tissues are often enlarged – hepatomegaly, cardiomegaly,

thickened peripheral nerves, macroglossia

Amyloid in the kidneyAmyloid protein is deposited in the basement membrane of glomerular capillaries and

renal arterioles

increased permeability of capillaries proteinuria and pogressive renal disease

Later, capillaries become obliterated glomeruli replaced by amyloid protein

secondary atrophy of tubules interstitial fibrosis secondary ischaemic changes

• Affected tissue is firm and less flexible therefore affected blood vessels do not

contstrict normally and tend to bleed

Diagnostic biopsy may be performed

1. Which of the following best explains why Amyloid can be identified in tissues?

1. it is derived from precursor proteins in plasma2. it is an insoluble substance3. its chemical composition is variable4. it is deposited extra-cellularly5. it produces a brown colour with iodine

2. A liver biopsy in a patient suspected of having Amyloidosis is sent to the Pathology Department of a General Hospital in Sri Lanka. The entire tissue was processed. A pinkish extra-cellular material is seen in a section stained with haematoxylin and eosin.

Which of the following would be the most suitable method to identify this substance as Amyloid, in the given setting?

1. Congo Red stain2. Immunohistochemical staining for AA protein.3. Iodine stain 4. Thioflavine immunofluoresence5. Electron microscopy

3. A patient who has had chronic osteomyelitits for several years presents with hepatomegaly. He is suspected of having Systemic Amyloidosis.

Which type of Amyloid protein is he most likely to have?

1. AL2. AA3. AF4. ATTR5. Aβ2m

4. A 50 year old patient presents with proteinuria of six months duration. He is suspected to have Amyloidosis and a renal biopsy is performed.

Which of the following is the most probable site of Amyloid deposition in the kidney?

1. The interstitial tissue2. The tubular epithelial cells3. The endothelial cells4. The basement membrane of blood vessels5. The Bowmans capsule

5.Which of the following are true regarding clinical presentations of amyloidosis.

A. Amyloidosis of the liver causes hepatomegaly

B. Amyloidosis of the heart causes a restrictive cardiomyopathy

C. Amyloidosis of the kidneys causes proteinuria

(a) A (b) B (c ) C (d) None of the above(e) all of the above

6. Amyloidosis should be clinically suspected in the following situations.

A When a patient with long-standing rheumatoid arthritis develops hepatomegaly.B. When a patient with multiple myeloma develops severe proteinuria and Nephrotic

SyndromeC. When a patient with chronic osteomyelitis develops splenomegaly.D. When a patient with lobar pneumonia develops a pleural effusion.(1) A, B (2) A, C (3 ) B, D (4) A, B, C (5) B, C