Hypersensitivity Reactions · Pathology

Fibrinoid necrosis in small blood vessels is a histological hallmark of which hypersensitivity reaction?

  1. Type I
  2. Type II
  3. Type III
  4. Type IV
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Correct answer: Type III

Fibrinoid necrosis occurs in Type III hypersensitivity (vasculitis) when immune complexes and complement activation cause severe damage to the vessel wall. The leakage of plasma proteins, including fibrin, creates a bright pink, smudgy appearance on H&E stains.

Difficulty: Medium Question 10 of 20

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