Amyloidosis, Samples, and Diagnosis
Amyloidosis
Sample for Diagnosis of amyloidosis
- Gingiva: The gingival biopsy is positive in one-half to two-thirds of the cases.
- Rectum: The rectal biopsy is also positive in two-thirds of the cases.
- Kidney: A needle biopsy of the kidney is needed when gingival and rectal biopsies are not helpful.
- Skin: The skin biopsy may also be the site for amyloidosis diagnosis.
- Another site depends upon the involvement of other organs like GIT, spleen, and respiratory tracts.
- Serum and urine will show a monoclonal band on electrophoresis.
Definition of amyloidosis:
- Amyloidosis is a disorder of protein metabolism in which there are extracellular deposition pathologic insoluble fibrillary proteins in organs and tissues.
- Amyloidosis is the accumulation of the various insoluble fibrillary proteins between the tissue cells and gives rise to loss of the function of that organ.
- The fibrils generally represent proteolytic fragments of various plasma proteins and possess the structure of a β-pleated sheet.
- These β-pleated sheets are insoluble and resentence to proteolysis.
- The term amyloidosis is a misnomer, as originally thought that fibrils are starch-like in nature.
Pathophysiology of Amyloidosis:
- Amyloid is a Greek word meaning resembling starch because of staining with iodine and other dyes.
- Amyloidosis is a rare disease that occurs when a substance called amyloid (folded protein) builds up in various organs.
- The most common precursor proteins are immunoglobulin light chains.
- Amyloid is a pathological extracellular deposit that appears structureless and translucent, and it stains with iodine and various dyes.
- Its affinity with congo red is the basis of its definition and identification in the biopsy material.
- Under polarized light, amyloid with congo red shows apple-green fluorescence.
- Amyloid exerts pressure on the vital organs and leads to death.
- Amyloid is an abnormal protein that is usually produced in bone marrow, is an insoluble protein, and can be deposited in any tissue or organ.
- Amyloidosis is usually seen in the heart, liver, spleen, kidney, nervous system, and gastrointestinal system.
- Amyloid is an extracellular deposit of the amyloid protein.
- Hematoxylin and eosine stains show amyloid as amorphous, eosinophilic, hyaline extracellular substances.
- It encroaches on the adjacent cells and leads to atrophy of the surrounding cells.
- This is not a single disease; rather, it is a group of diseases sharing deposition of similar appearing proteins.
- Biochemistry of the amyloid:
- Amyloid is an insoluble protein resistant to normal proteolysis due to its β- conformation.
- The above feature is common to all types of amyloid, whatever is their composition.
- Amyloid fibrils may have multiple soluble plasma protein precursors modified by proteolysis to make them insoluble.
- The end result of this insoluble amyloid is the disease called amyloidosis.
- This deposit may be local or systemic.
- This amyloid material exerts local pressure, and the result is the death of the tissue.
Structure of the amyloid:
- Amyloid by electron microscopy is nonbranching fibrils 7.5 to 10 nm in width.
- The Electron microscopic picture shows:
- Two fibrillary components with characteristic periodicity.
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- One rod-like structure P-component is a glycoprotein on their head.
- This has a hollow core and is a pentamer.
- These fibrillary components are crossed β-pleated sheets, seen by X-Ray crystallography.
- Any fibrillar proteins deposited in the tissue which look like β-pleated sheets are amyloid.
- 95% of the amyloid is fibril proteins, and the rest 5% consists of P components or glycoproteins.
Chemical nature of the amyloid:
- There are roughly 15 amyloid proteins, and three of these are very common.
- Amyloid light chain (AL). These are derived from the plasma cells and consist of immunoglobulin light chains.
- This may be light chain κ or λ.
- This is seen in plasma cell neoplasm, lymphomas, cardiomyopathy, macroglossia, and hepatosplenomegaly.
- Amyloid-associated amyloid (AA). These are non-immunoglobulin proteins synthesized by the liver.
- This is also called serum amyloid-A protein (SAA).
- This is secondary amyloidosis. This is seen in:
- Chronic diseases like tuberculosis, bronchiectasis, Crohn’s disease, nephrotic syndrome, cardiomyopathy, and rheumatoid arthritis.
- αβ amyloid is a β-precursor protein and found in:
- Patients with Alzheimer’s disease.
- Type 2 diabetes.
- β2 Microglobulin amyloid is β2 Microglobulin and found in:
- Renal failure.
- Musculoskeletal diseases.
- Long-term hemodialysis.
- ATTR amyloid is transthyretin. It is found in:
- Neuropathy.
- Cardiomyopathy.
- Senile amyloidosis with cardiomyopathy.
- Amyloid light chain (AL). These are derived from the plasma cells and consist of immunoglobulin light chains.
Clinically Amyloidoses are grouped into:
- Primary Amyloidosis:
- It consists of a portion of the light chain, so-called an immunoglobulin light chain (AL) amyloidosis. This is produced spontaneously from the plasma cells, which may be seen in the cancer of bone marrow like Multiple myelomas.
- Amyloidosis is associated with multiple myeloma.
- These two types are associated with the increasing number of plasma cells (Plasmacytosis).
- There is the monoclonal proliferation of the cells giving two identical light chains known as AL amyloid.
- This primary amyloidosis is derived from the variable region of the immunoglobulin’s light chains, and the most common is lambda (λ).
- Amyloidosis is associated with multiple myeloma:
- Above groups 1 and 2 are associated with plasmacytosis in the bone marrow, and these will produce an excess of the light chain of the immunoglobulins called AL amyloidosis.
- Multiple myeloma is associated with 20% to 30% of the cases.
- The monoclonal peak in serum and urine is seen in 50% of the cases by electrophoresis.
- Immunoelectrophoresis is positive in the serum and urine in about 90% of the cases.
- Secondary Amyloidosis (Reactive systemic):
- It results from a chronic illness like tuberculosis, osteomyelitis, or other chronic inflammatory diseases like rheumatoid arthritis and ankylosing spondylitis.
- This is called secondary amyloidosis or AA amyloidosis.
- AA protein is an amino-terminal fragment of serum amyloid A protein with a Molecular weight of 220 to 235 kDa and forms a complex with HDL and circulates in the blood.
- AA amyloid is an acute-phase protein, that increases rapidly in infectious or noninfectious inflammation.
- These are associated with chronic inflammatory diseases.
- Rheumatoid arthritis has an incidence of 20% and Other inflammatory joint diseases.
- AA is also deposited in chronic suppurative and granulomatous diseases (TB, osteomyelitis).
- Deposits of AA amyloid most frequently occur in the kidney, liver, and spleen.
- AA may deposit in nonlymphoid tumors like renal and gastric carcinoma. This is also found in Hodgkin’s lymphoma.
- There may be nephrotic syndrome and hepatosplenomegaly.
- Aging (senile amyloidosis):
- Amyloidosis is associated with the aging process.
- This is also called senile amyloidosis, and most often, the heart is involved, called senile cardiac amyloidosis.
- This may also be found in the pancreas and brain.
- Nodular or infiltrative amyloid deposits s are seen in the skin, lungs, trachea, and endocrine organs (thyroid medullary carcinoma) and in long-standing diabetics (pancreas).
- These patients are usually asymptomatic except for cardiac form.
- Familial Amyloidosis:
- These are autosomally dominant transmitted diseases where the mutant protein forms amyloid fibrils, usually starting in middle age.
- The most common form is a mutant – transthyretin, a tetrameric protein with four identical subunits.
- This is a transport protein for thyroxine and retinol-binding protein, and it is mainly synthesized in the liver.
- It can cause amyloid polyneuropathy or cardiomyopathy. It can involve kidneys and blood vessels.
Classification of Amyloidosis:
- Amyloidosis may be:
- Generalized or systemic: Multiple organs are involved.
- Primary amyloidosis when there is a disturbance of the immune system.
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- Seen in multiple myeloma and monoclonal B-cell proliferation.
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- Secondary amyloidosis when the cause is a chronic inflammatory disease.
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- Reactive systemic amyloidosis.
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- Primary amyloidosis when there is a disturbance of the immune system.
- Localized: In this type, only one organ is involved, like amyloidosis of the heart.
- Senile cerebral changes were seen in Alzheimer’s disease.
- In medullary carcinoma of the thyroid (endocrine).
- Islets of Langerhans (endocrine).
- Isolated atrial amyloidosis.
- Hereditary or familial amyloidosis is a separate group with a different pattern of organ involvement.
- Familial Mediterranian fever.
- Familial amyloidotic neuropathies.
- Senile systemic amyloidosis. This is most often found in the heart, called senile cardiac amyloid. This may also be seen in the brain and pancreas.
- Nodular or infiltrative amyloid deposits may be seen in the skin, lungs, and trachea.
- It may be seen in long-standing diabetes mellitus in the pancreas.
- It may be seen in the thyroid in the case of medullary carcinoma.
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- These forms are asymptomatic except for the heart.
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The sign and symptoms of Amyloidosis:
- Except for the familial type of amyloidosis, it is seen in older patients with an average age of 60 years.
- These depend upon the organ involved.
- There are severe fatigue and weakness.
- There is shortness of breath.
- There may be diarrhea with blood, and sometimes there is constipation.
- There may be swelling of the ankles and legs.
- The skin may show thickening or easy bruising and patches around the eyes.
- The most commonly involved organs are Kidney and heart.
- There may be an irregular heartbeat.
- The patient may develop difficulty in swallowing.
- Kidney involvement leads to nephrotic syndrome. There may or may not be raised creatinine and blood urea.
- There is the involvement of the kidney in 90 to 96 % of the cases with the amyloid type of AA.
- Immunoglobulin light-associated (AL) primary amyloidosis gives the S/S of the organ involved.
- Kidneys’ involvement will show proteinuria and nephrotic syndrome.
- The cardiovascular system shows cardiac failure.
- Carpal tunnel syndrome with weakness and paresthesia of the hands may be an early feature.
- Sensory neuropathies are common.
- On physical examination shows hepatomegaly, rarely splenomegaly, cardiomyopathy, polyneuropathy, and bruising may be seen.
- Macroglossia may be seen in 20% of the cases.
- Familial transthyretin-associated amyloidosis (ATTR):
- There is peripheral sensorimotor and autonomic neuropathy is more common with symptoms of diarrhea and weight loss.
- Macroglossia is not seen in this type.
- Cardiac dysfunction is of conduction.
- Reactive or secondary (AA) amyloidosis:
- This is usually due to chronic inflammatory conditions like rheumatoid arthritis, inflammatory bowel disease, and untreated Mediterranian fever.
- In developed countries, it has been in patients with tuberculosis, bronchiectasis, and osteomyelitis.
- Local amyloidosis: There is the local deposit of amyloid fibrils in various organs like the skin, heart, and brain.
- In cerebral amyloidosis, there are intracerebral and cerebrovascular amyloid deposits seen in Alzheimer’s disease.
- In hereditary spongiform encephalopathies cerebral several amyloid plaques are seen.
Risk factors leading to amyloidosis:
- Age, the most common age group involved is 50 or older people except for the younger age group.
- In family history, some amyloidosis is hereditary.
- Sex, the majority of the patients are male.
- Dialysis of the patient also leads to amyloidosis.
- Chronic diseases predispose to amyloidosis.
Causes of amyloidosis:
- Leprosy in 1/3 of the cases.
- Chronic infections like osteomyelitis, and tuberculosis. Etc.
- Multiple myelomas.
- Other malignancies like renal cell carcinoma and lymphomas.
The complication of amyloidosis:
- Kidney, when involved, will ultimately lead to renal failure.
- Kidney size may be normal or enlarged.
- Amyloid deposits in the glomeruli.
- Amyloidosis is also seen in the interstitium and the wall of blood vessels.
- The cardiovascular system leads to heart failure and arrhythmias.
- The heart size may increase from minimum to moderate enlargement.
- Amyloid deposits are found in the myocardium.
- The spleen may be enlarged moderately to a large size.
- Amyloid deposit is limited to splenic follicles and giving sago spleen appearance.
- Liver amyloidosis causes massive enlargement.
- The amyloid deposit first appears in the space of Disse.
- Later on, encroach the adjacent liver parenchyma.
- In late stages involve the sinusoids.
- The Central nervous system leads to various types of complications like diarrhea, constipation, numbness of fingers, and dizziness.
Diagnosis of Amyloidosis:
- Take a biopsy from the clinically affected tissue.
- Congo-red test: Congo-red binds the amyloid and gives apple-green fluorescence under the polarized light. This test is positive in one-third of the primary amyloidosis and about two-thirds of the secondary amyloidosis of the patients.
- Fat aspiration from the subcutaneous tissue showed positivity in 75% of the cases.
- 85% positive in the AL amyloidosis from the abdominal subcutaneous fatty tissue.
- Gingival and rectal biopsy is positive in one-half to two-thirds of patients.
- In the case of kidney involvement, a needle biopsy of the kidney is needed.
- Bone biopsy is positive in 30% of the multiple myeloma cases.
- Live needle biopsy may be positive.
- In case of skin involvement, take the biopsy from the plaques.
- In carpal tunnel syndrome, a biopsy from the carpel tunnel tissue is positive in 90% of the cases.
- The biopsy may be taken from involved areas like GIT, spleen, and respiratory system.
- Immunohistochemical staining shows the reaction of fibrils with Kappa (κ) or lambda (λ) antisera.
- E/M is the most specific for the diagnosis of amyloidosis.
- Bone marrow may show an increased number of plasma cells in primary amyloidosis or lymphoproliferative disorders.
- Urine may show proteinuria and light chains in the AL amyloidosis.
- There may be paraproteinemia.
- Scintigraphy using the 123I-labelled serum amyloid P component is useful for diagnosing AL, ATTR, and AA amyloidosis. But this test is not available in most of the labs.
Treatment of Amyloidosis:
- There is no definite treatment or cure for amyloidosis.
- But treatment can limit the production of amyloid protein.
- There is the symptomatic treatment for nephrotic syndrome and cardiac failure.
- Colchicine may be helpful for familial Mediterranian fever.
- Chemotherapy may show some benefits in AL amyloidosis.
Prognosis of Amyloidosis:
- It depends upon the type of amyloidosis and the organ involved.
- In generalized amyloidosis, the prognosis is poor, with mean survival after the diagnosis is 1 to 3 years.
- Microscopic and focal deposits in older people are of no clinical significance.
- Widespread deposits are progressive and fatal.
- AL Amyloid patients with cardiac involvement have a worse prognosis and, in untreated cases, is less than the survival is one year.
- AA amyloid patients survive 2 to 4 years.
- ATTR amyloid patients survive for 15 years.
- For patients with multiple myeloma-associated amyloidoses, the prognosis is poor.
- Treatment is aimed at:
- Reducing the supply of precursor protein.
- Treat the bleeding problem.
- Increase the motility.