Paper I
Question
Define amyloid. Name the stains used for demonstration of amyloid.
Answer
Definition
- Amyloid is a pathologic extracellular proteinaceous substance deposited in tissues, composed of misfolded protein fibrils arranged in an abnormal, insoluble beta-pleated sheet configuration, which is resistant to degradation and progressively disrupts normal tissue architecture and function
Stains used for demonstration of amyloid
- Congo red stain — classic stain; shows apple-green birefringence under polarized light (gold standard)
- Crystal violet / Methyl violet — metachromatic staining (pink-violet)
- Thioflavin T/S — fluorescence under UV light
- Immunohistochemistry — for typing the specific amyloid protein (AL, AA, transthyretin, etc.)