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Amyloidosis

Amyloid

  • Family of extracellular proteins composed of B-pleated sheets
  • Mammalian systems have no enzyme to degrade these compounds (similar to silk ligatures)
  • Have apple-green birefringnce on polarised light after staining with Congo red

Classification

AL

 Amyloid Lymphocyte origin: Primary amyloid
Soluble precursor Ig light chains (esp from myeloma)
  1. Heart: restrictive cardiomyopathy
  2. Nerves: neuropathy
  3. Skin: may result in carpal tunnel syndrome
AA

Secondary/Reactive amyloid
From chronic conditions - macrophages secrete ILs that stimulate hepatocytes to secrete serum amyloid precursor protein (SAA)

  • Chronic infection: TB, syphillis, leprosy
  • Chronic inflammatory diseases: RhA, Crohns, UC
  • Neoplasms: Hodgkin's, renal cell carcionoma
  1. Kidney: walls renal arteries, GM, BM
  2. Liver: in sinusoidal space of Diss
  3. Spleen: forms"sago spleen"
AH/AB

Occurs with Alzheimer's disease with APP as precursor

 
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