Amyloidosis

General: A somewhat non-specific term indicating abnormal tissue deposition of protein. Has multiple causes and effects.

• Senile/age-related: May be systemic or localized. Atrial natriuretic peptide in the case of senile localized cardiac (isolated atrial) amyloidosis; common in the elderly.
• Primary: Plasma cell dyscrasias, including multiple myeloma. Monoclonal light chains.
• Secondary: Inflammatory conditions
• Hereditary:

The cardiovascular system is most commonly affected in the primary and age-related forms, and involves the myocardium, vessels, and valves. Usually associated with restriction due to poor ventricular compliance.

Types: Two amyloid components comprise each designated type, where A represents amyloidosis and the other letter or letters represents protein.

• AA (apo SAA): Systemic secondary amyloidosis (in the setting of chronic inflammation).
• AL (kappa or lambda light chains): Systemic primary amyloidosis (often in the setting of multiple myeloma).
• AH (IgG1): Systemic heavy chain amyloidosis.
• ATTR (transthyretin): Systemic hereditary or de novo amyloidosis (polyneuropathy or cardiomyopathy).
• AGel (Gelsolin): Finnish familial amyloidosis.
• AApoA1 (apoA1): Familial amyloid polyneuropathy.
• A(beta2)M (beta2-microglobulin): Systemic amyloidosis found with chronic dialysis (often in joint capsules, ligaments).
• A(beta) (A beta protein precursor): Localized cerebral amyloid.

Gross:

• Cardiac amyloidosis: Slightly enlarged heart with a stiff, rubbery, or waxy myocardium.

Microscopic:

• Cardiac amyloidosis: Myofibers surrounded by amorphous, eosinophilic extracellular material which is metachromatic with crystal violet stain and exhibits apple-green birefringence under polarized light with congo red stain.

Differential Diagnosis:

Stains:

• Positive: Congo red with classic apple-green birefringence under polarized light; should be done on THICK (~10 micron) sections, not the standard 3~5 micron sections.
• Negative:
• Suggested, focused panel: Immunohistochemistry for specific proteins are required for typing, but may not be indicated.

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Images:


Cases:

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