Fibrinoid necrosis

  • Definition: a type of necrosis characterized by small blood vessel injury with accumulation of fibrin and other plasma proteins.
  • Pathophysiology: vessel wall damage caused by immune complex deposition (e.g., due to type III hypersensitivity reaction) → fragmentation of collagenous and elastic fibers → leakage of fibrin and other plasma proteins
  • Microscopic appearance
    • Visible damage: thick walls with fragments of embedded cellular debris, serum, and fibrin
    • Affected necrotic areas stain intense red.
  • Examples