Amyloidosis

Overview

• Amyloid is misfolded protein that takes the form of a beta-pleated sheet
  • the protein cannot be degraded by cellular enzymes
  • results in accumulation in the extracellular space
  • the deposited mass of the misfolded protein is damaging to tissues
• Diagnosis made by demonstrating 
  • apple-green birefringence of Congo red stain under polarized light 
• Amyloid can form from a variety of proteins but the above characterisitic are shared properties
• Amyloid can be localized or systemic

Systemic Amyloidosis

• Affects the entire body and can be of primary or secondary cause
• Primary
  • result of AL amyloid deposition
    • derived from Ig light chain
    • classically seen in multiple myeloma
• Secondary
  • result of AA amyloid deposition
    • derived from acute phase reaction of inflammation 
      • associated with increased levels of IL-6
    • can see with rheumatoid arthritis or other forms of chronic inflammation
• Clinical findings
  • deposition in glomerulus
    • results in nephrotic syndrome
  • deposition in the heart
    • results in arrhythmias and/or restrictive cardiomyopathy
• deposition in liver, spleen, tongue, intestine

Localized Amyloidosis

• Affects only a specific organ