Amyloidosis

Amyloidosis

A medical condition resulting from aggregation of extracellularly deposited abnormal proteins called amyloid fibrils that cause damage to organs and tissues.
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Amyloidosis

Proteins aggregate and form fibrils called amyloid fibrils. These fibrils are insoluble, linear, rigid and measures approximately 7.5 to 10 nm in width & indefinite length.
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Classification of Amyloidosis
Chemical subtypes 95% of amyloid material consists of fibril protein and 5% is the P-component which is a glycoprotein similar to C-reactive protein. A- Chemically according to amyloid precursor protein amyloid is classified into: 1- AL (amyloid light chain) which is derived from the Ig light chain and deposited in the tissues of patients with plasma cell dyscrasias (like multiple myeloma). 2- AA (amyloid associate) which is derived from serum amyloid associated protein (SAA) synthesized by the liver in cases of chronic inflammations like bronchiectasis, Rheumatoid A, TB, osteomyelitis, abscesses.
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Classification of Amyloidosis

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Clinical Manifestations

Clinical Manifestations depend on which organ is affected: E.g. Heart: -Cardiomyopathy -Heart failure -Ischemic heart disease
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Renal: Proteinuria, nephrotic syndrome, renal failure leading to kidney transplant or dialysis. Muscle: Hypertrophy of muscles, macroglossia Skin: Nodules, plaques, easy bruising GI: Organomegaly (Hepatomegaly, splenomegaly), abnormal bowel movement usually constipation, malabsorption
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Senile cerebral amyloidosis in patients with Alzheimer’s Disease Alzheimer's disease (AD) is a progressive degenerative disease of the brain from which there is no recovery. The disease slowly attacks nerve cells in all parts of the cortex of the brain and some surrounding structures, thereby impairing a person's movement and memory. Ultimately, patient loses memory and many other mental functions.
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* CNS/Neuro: Neuropathy, dementia.

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Diagnosis
Clinical: Unexplained medical disorder and you suspect amyloidosis: e.g heart failure, proteinuria, hepatic dysfunction Ultimately, you need tissue biopsy from: Abdominal fat, kidney, oral mucosa, rectal mucosa. Bone marrow biopsy
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Characteristics common to all amyloid subtypes
Hematoxylin and Eosin (HE) staining results in an extracellular deposition of amorphous eosinophilic appearance when viewed on light microscopy.
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* Spleen amyloidosis


* Kidney: Histologically amyloid is deposited primarily in the glomeruli (widening of the mesangial matrix with homogenous, structureless material + thickening of basement membrane).
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Normal glomerulus
Amyloidosis

Special tests for diagnosis of amyloidosis

Diagnosis of amyloidosis is by a special stain for amyloidosis (like Congo red, Lugol’s iodine, Immunofluorescent stain), electron microscopy. * 2014


Congo red staining results in bright green fluorescence/birefringe apple green color when viewed under special microscope (containing polarized light).
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* Congo red stain (apple green color)

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Immunofluorescent stain



Definite diagnosis is by electron microscope; non-branching fibrils of indefinite length and a diameter of approximately 7.5 - 10 nm.
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