A 65-year-old man suffers an acute myocardial infarction. Electron microscopy of the irreversibly injured myocardium shows mitochondria with large amorphous matrix densities. Which of the following best explains the significance of this finding?
- A It represents calcium accumulation and marks the point of no return in cell injury ✓
- B It indicates reversible injury and the cells can fully recover
- C It is a hallmark of apoptosis with cytochrome c release
- D It indicates fatty change due to impaired beta-oxidation
Correct answer: A. It represents calcium accumulation and marks the point of no return in cell injury
Explanation
Amorphous matrix densities in mitochondria represent calcium phosphate deposits and indicate irreversible injury, marking the point of no return. This occurs after prolonged ischemia when ATP depletion and membrane damage lead to massive calcium influx. It is not seen in reversible injury, apoptosis (which shows normal mitochondria early), or fatty change.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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