Amyloidosis

Slide 1 · Amyloidosis

Protein misfolding, extracellular deposits, organ injury and diagnosis

Mechanisms • morphology • clinicopathologic correlation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Define amyloid and explain its shared fibrillar architecture.

Differentiate AL, ATTR and AA by precursor and mechanism.

Recognize tissue morphology, diagnostic stains and organ effects.

Select confirmatory tests and interpret clinicopathologic patterns.

Slide 3 · Amyloidosis denotes a family of deposition disorders

Proteins with aggregation propensity form insoluble fibrils.

Deposits accumulate extracellularly in tissues and organs.

Progressive accumulation damages tissues and compromises function.

The same morphologic pattern can arise from distinct precursor proteins.

Slide 4 · Molecular route from soluble protein to amyloid

Soluble precursor

Misfolded monomers

Oligomeric aggregates

Extracellular fibrils

A soluble precursor becomes unstable or misfolded.

Monomers associate into oligomers and larger aggregates.

Insoluble fibrils accumulate in the extracellular compartment.

The identity of the precursor determines the amyloid type.

Slide 5 · “Amyloid” is a historical misnomer

Early staining behavior was interpreted as resembling starch (amylose).

The deposits are proteinaceous—not starch.

Bound proteoglycans and glycosaminoglycans contribute to histochemical behavior.

Serum amyloid P component is associated with deposits.

Slide 6 · The extracellular location drives the lesion

SCHEMATIC — NOT A TISSUE IMAGE

Expanding extracellular amyloid

Extracellular material displaces adjacent cells

Amyloid appears between cells and adjacent to basement membranes.

Increasing deposits encroach on neighboring functional tissue.

Affected cells may atrophy or disappear with progression.

Slide 7 · Distribution and burden determine manifestations

Localized

Restricted to one site

May form a nodule

Often discovered locally

Systemic

More than one organ may be involved

Renal and cardiac disease can dominate

May be clinically occult early

Slide 8 · Shared histology does not imply shared chemistry

More than 40 distinct proteins can form amyloid.

The deposited proteins have characteristic fibrillar organization.

Routine light microscopy cannot reliably assign biochemical type.

Typing is necessary to identify the underlying disease process.

Slide 9 · Amyloid fibrils have a characteristic ultrastructure

Protofilament assemblies

Cross-β structure

Nonbranching fibrils

Shared Congo red property

Electron microscopy reveals continuous, nonbranching fibrils.

Fibril diameter is approximately 8–10 nm.

Protofilaments have a β-pleated sheet arrangement.

The common conformation helps explain staining similarities.

Slide 10 · Amyloid deposits include nonfibrillar components

Fibril core

Predominant protein fraction

Amyloidogenic precursor-derived

Defines biochemical amyloid type

Associated constituents

Serum amyloid P and glycoproteins

Proteoglycans/glycosaminoglycans

Contribute to deposit properties

Slide 11 · Three major amyloid types identify different precursors

Type

Precursor

Typical context

AL

Ig light chain

Clonal plasma cell disorder

ATTR

Transthyretin

Aging or inherited TTR variant

AA

Serum amyloid A

Sustained inflammation

Slide 12 · AL identifies immunoglobulin light-chain amyloid

Clonal plasma cells

Free Ig light chains

Amyloidogenic sequences

AL tissue deposits

Amyloid may contain intact light chains or light-chain fragments.

The precursor is secreted by a monoclonal plasma cell population.

λ light chains predominate account; κ may also form amyloid.

AL frequently has a systemic distribution.

Slide 13 · ATTR identifies transthyretin-derived amyloid

Transthyretin

Aging or TTR variant

Misfolding / aggregation

ATTR deposits

Transthyretin transports thyroxine and retinol.

Wild-type TTR can aggregate with aging.

Inherited TTR variants can favor protein misfolding.

Deposits often target heart, peripheral nerves or connective tissues.

Slide 14 · AA identifies an inflammation-linked amyloid

Chronic inflammation

IL-1 / IL-6 signaling

Hepatic SAA production

AA fibril deposition

The AA fibril protein is derived from circulating serum amyloid A.

Hepatocytes synthesize SAA as an acute-phase reactant.

SAA production increases in chronic inflammatory states.

Persistent supply plus altered processing favors AA deposition.

Slide 15 · Other proteins also form amyloid

Deposit

Precursor/source

Example

Aβ

Amyloid precursor protein

Alzheimer disease

Aβ₂M

β₂-microglobulin

Long-term hemodialysis

AIAPP

Islet amyloid polypeptide

Type 2 diabetes

ACal

Calcitonin

Medullary thyroid carcinoma

Slide 16 · Classify amyloidosis by distribution and protein type

Clinical amyloid deposit

Determine distribution

Identify fibril protein

Establish precursor disorder

Systemic: Amyloidogenic protein or deposits affect multiple organs.

Localized: Deposits remain in an individual site or organ.

Hereditary: A molecular predisposition may influence the precursor.

An etiologic diagnosis requires protein identification and clinical context.

Slide 17 · Systemic and localized are separate axes from type

Anatomic classification

Single site or multiple organs

Defines extent of involvement

Guides organ assessment

Biochemical classification

AL, AA, ATTR, other proteins

Identifies deposited precursor

Guides investigation of mechanism

Slide 18 · Protein homeostasis ordinarily limits amyloid

Misfolded protein

Proteasome / macrophage disposal

Persistent amyloidogenic pool

Extracellular deposition

Intracellular misfolded proteins undergo proteasomal degradation.

Macrophages help clear extracellular misfolded proteins.

Failure of these processes allows amyloidogenic material to persist.

Fibril formation reflects supply, instability and impaired clearance.

Slide 19 · Mechanism I: Excess production of a normal precursor

Increased precursor supply

More misfolding-prone substrate

Aggregation

AL or AA deposition

Some normal proteins can misfold when their concentration rises.

Clonal plasma cells can supply large quantities of light chain.

Inflammation can sustain high circulating SAA concentrations.

Production outpaces effective degradation or clearance.

Slide 20 · Mechanism II: Inherited protein instability

Variant TTR

Reduced folding stability

Misfolded intermediate

ATTRv fibrils

Variants can alter the folding propensity of an otherwise normal protein.

Variant transthyretin exemplifies genetically mediated amyloidogenesis.

Different variants may have different organ preferences.

A mutation does not guarantee identical phenotype in all carriers.

Slide 21 · Mechanism III: Aging-associated protein misfolding

Wild-type TTR

Age-associated aggregation

Extracellular fibrils

ATTRwt in heart / ligaments

Unmutated transthyretin can form amyloid in older adults.

The heart is a major site of ATTRwt deposition.

Connective tissues, including ligaments, can also be affected.

This is distinct from autosomal dominant variant ATTR.

Slide 22 · Amyloid generation has multiple entry points

Mechanism

Driver

Fibril

Clonal production

Abnormal Ig light-chain supply

AL

Inflammatory production

Increased SAA synthesis

AA

Inherited instability

Variant TTR

ATTRv

Age-associated instability

Wild-type TTR aggregation

ATTRwt

Slide 23 · Amyloid injures organs by replacing functioning tissue

SCHEMATIC — NOT A TISSUE IMAGE

Expanding extracellular amyloid

Extracellular material displaces adjacent cells

Extracellular deposits distort the local architecture.

Compression and pressure atrophy diminish viable parenchyma.

Vascular and basement-membrane deposits impede normal exchange.

Slide 24 · Additional cellular effects may contribute to injury

Amyloidogenic species

Signaling perturbation

ROS / Ca²⁺ disturbance

Cellular dysfunction

Some amyloidogenic proteins may alter intracellular signaling.

Increased reactive oxygen species have been implicated.

Abnormal calcium homeostasis may compromise cell function.

These as possible adjuncts to architectural disruption.

Slide 25 · Amyloid appears as extracellular hyaline on H&E

What H&E suggests

Amorphous extracellular material

Expanding interstitial/basement-membrane deposits

Compression of neighboring cells

What H&E cannot prove

Specificity for amyloid

Amyloid fibril protein identity

Exclusion of collagen or fibrin

Slide 26 · Congo red provides the key tissue stain

Ordinary light

Pink–red Congo red-positive deposits

Localizes suspected amyloid

Interpret with tissue morphology

Polarized light

Characteristic apple-green birefringence

Reflects ordered fibrillar conformation

Shared across amyloid types

Slide 27 · Polarized Congo red reveals birefringence

Ordinary transmitted light

Polarized illumination

Pink–red deposits

Apple-green birefringence

Schematic of optical appearance only; Not a polarized tissue photomicrograph.

Slide 28 · Ultrastructure can support amyloid identification

Extracellular deposits

EM: Nonbranching fibrils

Compatible amyloid structure

Protein typing needed

Electron microscopy shows randomly arranged, fine fibrils.

The fibrils are nonbranching and approximately 8–10 nm wide.

This supports an amyloid diagnosis when light microscopy is uncertain.

Electron microscopy does not by itself identify precursor protein.

Slide 29 · Protein typing is different from deposit recognition

Diagnostic question

Approach

Interpretation

Is this amyloid?

Histology + Congo red

Deposit identification

Which protein?

IHC or mass spectrometry

Fibril type

What causes it?

Clinical and laboratory correlation

Underlying disorder

Slide 30 · AL originates in a clonal plasma-cell population

Plasma-cell clone

Monoclonal light chain

Sequence-specific misfolding

Systemic AL deposition

A monoclonal clone produces an immunoglobulin light chain.

Intrinsic sequence-dependent properties promote amyloid formation.

Many patients lack overt multiple myeloma.

Secreted abnormal protein may be the main clinical consequence.

Slide 31 · AL amyloidosis is not synonymous with myeloma

AL with myeloma

Recognizable plasma-cell tumor

Light chains may appear in serum/urine

Amyloid may complicate tumor

AL without overt myeloma

No classic bulky neoplasm required

Small clone can produce harmful protein

Amyloid drives organ disease

Slide 32 · Free light chains are clues, not sufficient proof

Free light chain

Serum / urinary detection

Not always amyloidogenic

Only some chains form AL

Clonal cells can release unpaired κ or λ light chains.

Small light chains may circulate and appear in urine as Bence Jones protein.

Most myeloma patients with free light chains do not develop amyloid.

Light-chain sequence influences amyloidogenic propensity.

Slide 33 · AL organ involvement cannot be inferred from clone size

Organ deposition may dominate the phenotype despite limited marrow disease.

Heart, kidneys, gastrointestinal tract and nerves may be involved.

Tongue, skin and respiratory tissues can be affected.

Assessment must focus on target-organ manifestations.

Slide 34 · ATTRwt: Wild-type protein in an aging host

Normal TTR sequence

Age-associated misfolding

ATTRwt fibrils

Heart / ligament deposits

Wild-type transthyretin can misfold and aggregate.

Cardiac involvement predominates in the source description.

Connective-tissue deposits may occur in ligaments.

Older men as a common affected population.

Slide 35 · ATTRv: A heritable protein misfolding disorder

Inherited TTR variant

Abnormal protein stability

Amyloid deposits

Neuropathy ± cardiomyopathy

A pathogenic TTR variant predisposes the protein to aggregation.

Inheritance is autosomal dominant.

Peripheral/autonomic neuropathy or cardiac disease may predominate.

Clinical expression varies considerably among carriers.

Slide 36 · Different TTR variants favor different tissues

Neuropathy-predominant ATTRv

Peripheral nerve deposits

Autonomic nerve involvement

Familial amyloid polyneuropathy

Cardiac-predominant ATTRv

Myocardial deposition

Restrictive physiology may follow

Hereditary cardiac amyloidosis

Slide 37 · Wild-type and variant ATTR: Critical distinctions

Feature

ATTRwt

ATTRv

TTR sequence

Wild-type

Variant

Underlying driver

Age-associated misfolding

Inherited sequence change

Typical involvement

Heart; Connective tissues

Heart and/or nerves

Inheritance

Not mendelian TTR mutation

Autosomal dominant

Slide 38 · AA follows persistent inflammatory signaling

Chronic inflammation

IL-1 / IL-6

SAA from hepatocytes

AA deposition

Macrophage-associated IL-1 and IL-6 stimulate hepatic SAA synthesis.

Chronic inflammation maintains elevated SAA concentrations.

Normally SAA is metabolized to soluble products.

A subset of patients develop insoluble AA fibril deposits.

Slide 39 · AA associations reflect chronic inflammatory load

Source of inflammation

Robbins examples

Autoimmune / rheumatic

Rheumatoid arthritis; Ankylosing spondylitis

Inflammatory bowel disease

Crohn disease; Ulcerative colitis

Chronic infections

Tuberculosis; Osteomyelitis; Bronchiectasis

Other settings

Repeated skin infections; Selected tumors

Slide 40 · Raised SAA alone does not guarantee AA amyloid

Persistent SAA excess

Impaired/altered proteolysis

Insoluble AA fragments

Systemic deposition

SAA is normally degraded by macrophage-derived enzymes.

Excess synthesis may combine with incomplete proteolytic degradation.

Inherited molecular differences in SAA may alter degradation susceptibility.

The source presents processing defects as possible explanations.

Slide 41 · Treating inflammation changed AA epidemiology

Earlier prominent associations

Tuberculosis

Bronchiectasis

Chronic osteomyelitis

More prominent contemporary settings

Rheumatoid arthritis

Other connective-tissue disorders

Inflammatory bowel disease

Slide 42 · Familial Mediterranean fever can lead to AA

Pyrin-related dysregulation

Excess IL-1 / inflammation

SAA overproduction

AA amyloidosis

Familial Mediterranean fever is an autosomal recessive autoinflammatory syndrome.

Pyrin-associated inflammasome dysregulation drives excess IL-1.

Recurrent fever and serosal inflammation create persistent inflammatory exposure.

Systemic deposits are of the AA type, not ATTR.

Slide 43 · Dialysis-associated amyloid uses β₂-microglobulin

β₂-microglobulin retention

Long-term dialysis exposure

Articular / periarticular deposits

Carpal tunnel syndrome

β₂-microglobulin is a component of MHC class I molecules.

Long-standing impaired clearance permits circulating accumulation.

Deposits favor joints, tendons, ligaments and adjacent soft tissues.

Improved dialysis filters have reduced this complication.

Slide 44 · Localized nodular amyloid may resemble a mass

Deposits can be confined to a single tissue without systemic involvement.

Examples include lung, larynx, skin, bladder, tongue and periorbital tissue.

Peripheral plasma cells and lymphocytes may accompany a nodule.

Some localized deposits are AL-related.

Slide 45 · Endocrine amyloid is often localized

Context

Amyloid protein

Role

Medullary thyroid carcinoma

Calcitonin (ACal)

Diagnostic morphology

Type 2 diabetic islets

Islet amyloid polypeptide (AIAPP)

Localized islet deposits

Selected endocrine tumors

Hormone-related / other proteins

Context-dependent deposits

Slide 46 · Amyloid-β is a localized cerebral deposition process

Amyloid precursor protein

Proteolytic processing

Aβ deposition

Cerebral plaques / vessels

Amyloid-β derives from cleavage of amyloid precursor protein.

Deposits contribute to plaques in Alzheimer disease.

Amyloid can also accumulate in cerebral vascular walls.

This should not be conflated with systemic AL, ATTR or AA disease.

Slide 47 · Distribution patterns overlap across amyloid types

AA often involves

Kidneys

Liver and spleen

Lymph nodes; Adrenals; Thyroid

AL often involves

Heart

Gastrointestinal and respiratory sites

Nerves; Skin; Tongue

Slide 48 · Gross amyloid appearance is variable

Minimal gross change

No reliable enlargement

Appearance may be inconspicuous

Tissue diagnosis still possible

Advanced deposition

Organ enlargement may develop

Gray, waxy, firm parenchyma

Function may be impaired

Slide 49 · The renal glomerulus is a major amyloid target

SCHEMATIC — NOT A TISSUE IMAGE

Glomerular tuft

Mesangial expansion and tuft distortion

Deposits develop in mesangial matrix and capillary basement-membrane regions.

Peritubular interstitium and small vessels may also be affected.

Amyloid restricts capillary lumen caliber.

Slide 50 · Glomerular amyloidosis progresses structurally

Mesangial expansion

Capillary narrowing

Tuft obliteration

Loss of filtration

Progressive deposition compromises the structure or function indicated by the final stage.

Slide 51 · Renal deposits produce proteinuria and failure

Anatomic lesion

Mesangial/capillary-wall deposits

Tuft distortion and impaired capillary function

Clinical consequence

Proteinuria → nephrotic syndrome

Progressive kidney failure

Slide 52 · The spleen has two classic deposition patterns

Sago spleen

Predominantly white-pulp follicles

Tapioca-like granules

Follicle-centered appearance

Lardaceous spleen

Predominantly red-pulp framework

Confluent, map-like deposits

Wider pulp involvement

Slide 53 · Hepatic amyloid begins in the space of Disse

SCHEMATIC — NOT A TISSUE IMAGE

Sinusoidal interface / space of Disse

Deposits accumulate between sinusoid and hepatocytes

Extracellular deposits begin along sinusoidal interfaces.

Progression compresses hepatocytes and narrows sinusoidal spaces.

Vascular involvement can accompany parenchymal disease.

Slide 54 · Cardiac amyloid infiltrates between myocytes

SCHEMATIC — NOT A TISSUE IMAGE

Myocyte bands separated by deposits

Interstitial deposits compress myocardium

Deposits may be subendocardial and interstitial within myocardium.

Expansion separates and compresses cardiac muscle fibers.

Subendocardial involvement can compromise the conduction system.

Slide 55 · Cardiac injury may be hemodynamic or electrical

Mechanical dysfunction

Amyloid between myocytes

Reduced myocardial compliance

Restrictive cardiomyopathy / heart failure

Electrical dysfunction

Subendocardial / conduction deposits

Conduction abnormalities

Potentially fatal arrhythmias

Slide 56 · Gastrointestinal effects depend on deposit location

Tongue involvement can cause macroglossia and impaired swallowing.

Stomach or intestinal deposition may lead to malabsorption.

Diarrhea and digestive disturbances can occur.

The same organ may harbor deposits without overt symptoms.

Slide 57 · Nerves, tendons and ligaments are clinically informative

ATTRv neuropathy

Peripheral and autonomic nerve deposits

Sensory/autonomic consequences

Genetically mediated TTR precursor

Dialysis-associated soft-tissue amyloid

Joints / tendons / ligaments

Median nerve compression at wrist

β₂-microglobulin precursor

Slide 58 · Amyloid can produce bleeding by two mechanisms

Vascular amyloid

Fragile blood vessels

Bleeding

AL: Possible factor X loss

Vascular-wall deposits increase vessel fragility.

Bleeding can occur after minor trauma or spontaneously.

Some AL amyloid binds and inactivates coagulation factor X.

Anatomic fragility and coagulopathy are distinct contributors.

Slide 59 · The initial clinical presentation can be nonspecific

Fatigue or weakness may precede organ-specific recognition.

Weight loss, lightheadedness and syncope can occur.

Later manifestations often arise from renal, cardiac or gastrointestinal injury.

Clinical recognition requires connecting symptoms to possible tissue deposits.

Slide 60 · Tissue confirmation is central to diagnosis

Clinical suspicion

Sample suitable tissue

Congo red + polarized microscopy

Protein typing

Diagnosis depends on histologic demonstration of amyloid deposits.

An affected-organ biopsy may be selected when clinically indicated.

Rectal or gingival biopsies are described for systemic evaluation.

Sampling strategy depends on suspected site and procedural considerations.

Slide 61 · Abdominal fat sampling offers a less invasive site

Positive aspirate

Demonstrates Congo red-positive material

Supports systemic involvement

Requires fibril typing

Negative aspirate

Does not reliably exclude amyloid

May require another biopsy site

Interpret with clinical suspicion

Slide 62 · Suspected AL requires monoclonal protein evaluation

Tissue amyloid

Serum / urine protein studies

Marrow assessment

Correlate with AL typing

Examine serum and urine for a monoclonal immunoglobulin/light chain.

Protein electrophoresis and immunologic methods are discussed.

Bone marrow examination may reveal monoclonal plasma cells.

A clone supports the mechanism but does not substitute for amyloid typing.

Slide 63 · A diagnostic workflow links deposit and mechanism

Confirm amyloid deposit

Type deposited protein

Investigate upstream cause

Assess organ dysfunction

First establish amyloid in a suitable specimen.

Determine biochemical fibril type using available typing methods.

Investigate corresponding precursor source or inherited/inflammatory driver.

Assess organs damaged by deposition.

Slide 64 · Do not assign amyloid type from organ distribution

Unsafe shortcut

“Heart disease means ATTR”

“Myeloma means biopsy must be AL”

“Kidney disease proves AA”

Defensible interpretation

Recognize Congo red-positive deposit

Type amyloid protein in tissue

Integrate pathology with plasma-cell and TTR evaluation

Slide 65 · Interpreting biopsy material: Diagnostic pitfalls

Potential pitfall

Corrective step

H&E “hyaline” assumed amyloid

Use Congo red and polarized examination

Congo red assumed to define type

Perform fibril typing

Negative small sample taken as exclusion

Consider tissue/site adequacy

Organ pattern substituted for chemistry

Integrate typing and cause

Slide 66 · Clinical example: Proteinuria plus plasma-cell clone

CLINICAL SCENARIO

A patient develops progressive proteinuria and biopsy-proven amyloid.

A monoclonal light chain is subsequently identified.

AL becomes an important mechanistic hypothesis.

Confirm the deposited amyloid type before attributing disease to the clone.

What two links establish the causal diagnosis?

Tissue amyloid identification + fibril typing, then evidence of a corresponding plasma-cell source.

Slide 67 · Clinical example: Inflammation plus renal amyloid

CLINICAL SCENARIO

A patient with chronic inflammatory arthritis develops nephrotic syndrome.

Renal histology demonstrates Congo red-positive deposits.

Persistent SAA production makes AA mechanistically plausible.

The fibril protein must still be identified.

What mechanism unites the systemic disease and renal lesion?

Inflammation-driven SAA elevation, followed by AA formation and glomerular deposition.

Slide 68 · Clinical example: Familial neuropathy with amyloid

CLINICAL SCENARIO

A family has progressive peripheral and autonomic neuropathy.

Biopsy confirms amyloid deposition.

Inherited ATTRv is a major differential when family history supports it.

Protein typing and inherited TTR context resolve the mechanism.

Which precursor and inheritance pattern fit the vignette?

Variant transthyretin; Autosomal dominant.

Slide 69 · Clinical example: Older adult with stiff heart

CLINICAL SCENARIO

An older patient develops a restrictive cardiomyopathy phenotype.

Cardiac amyloid is identified during diagnostic assessment.

ATTRwt is a possible cause, but AL and variant ATTR remain considerations.

Protein typing prevents classification by age alone.

Why is the diagnosis not simply “senile cardiac amyloid”?

The clinical phenotype overlaps AL, ATTRwt and ATTRv; Biochemical type must be established.

Slide 70 · Clinical example: Dialysis and median nerve compression

CLINICAL SCENARIO

A patient on prolonged dialysis develops symptoms of carpal tunnel syndrome.

Amyloid deposition within periarticular soft tissue is identified.

β₂-microglobulin retention provides a mechanistic explanation.

This differs from AL, AA and ATTR precursors.

What deposited protein best links dialysis and carpal tunnel syndrome?

β₂-microglobulin (Aβ₂M).

Slide 71 · Prognosis is shaped by organ injury and amyloid type

Generalized amyloidosis can lead to severe organ dysfunction and death.

AL disease, especially myeloma-associated AL, as high risk.

The course of AA disease depends partly on control of its inflammatory driver.

Disease subtype and organ involvement are more informative than the label alone.

Slide 72 · Treatment logic follows the precursor mechanism

Type

Upstream process

Mechanistic treatment objective

AL

Clonal light-chain production

Reduce amyloidogenic light-chain source

AA

Inflammation → SAA synthesis

Suppress ongoing inflammatory drive

ATTR

Transthyretin misfolding

Limit aggregation of TTR

Slide 73 · Clinical outcomes follow the involved structure

Primary site

Structural consequence

Manifestation

Kidney

Glomerular tuft loss

Proteinuria / failure

Heart

Myocyte compression; Conduction injury

Heart failure / arrhythmia

GI tract / tongue

Parenchymal and interstitial infiltration

Malabsorption / macroglossia

Blood vessels

Wall fragility

Bleeding

Slide 74 · Synthesize precursor, deposit and phenotype

Identify fibrils

Type precursor

Explain production / misfolding

Relate to organ lesion

Identical Congo red behavior can reflect distinct precursor proteins.

Mechanism may involve protein excess, instability or incomplete degradation.

Extracellular accumulation perturbs tissue architecture.

Protein typing and systemic evaluation are complementary—not interchangeable.

Slide 75 · Five high-yield conclusions

Amyloidosis is a protein-folding and deposition disorder, not one protein disease.

Extracellular cross-β fibrils explain characteristic Congo red birefringence.

AL, ATTR and AA arise from different precursor pathways.

Renal and cardiac lesions can cause major morbidity and mortality.

Confirm tissue amyloid, type the protein and establish the clinical cause.

Slide 76 · Reference and source boundaries

Primary: Robbins, Cotran & Kumar, Pathologic Basis of Disease, 11th ed. (2026), Chapter 6, pp. 230–234.

Read with the amyloidosis sections on properties, biochemistry, classification, morphology and clinical features.

The supplied Markdown was used for content; original chapter PDF and reusable specimen images were not provided.

All constructed tissue/flow schematics in this deck are educational illustrations, not diagnostic images.