Learning Objective:

Explain the biochemical composition, mechanism of formation, tissue distribution, and clinical relevance of lipofuscin as a marker of normal aging.

Lipofuscin

Lipofuscin is a yellow-brown “wear-and-tear” intracellular pigment that accumulates progressively with normal aging, particularly in long-lived, post-mitotic cells.

• Composition: Aggregates of oxidized lipids and phospholipids bound to proteins
• Mechanism of formation: Results from lipid peroxidation of polyunsaturated fatty acids in cellular and organelle membranes, followed by incomplete lysosomal degradation
• Source: Byproduct of oxidative stress and normal cellular turnover

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Tissue Distribution

• Frequently identified at autopsy in older adults
• Common sites of accumulation include:
  • Heart
  • Liver
  • Kidney
  • Colon
  • Retina and other ocular tissues

Clinical Significance

• Serves as a histologic marker of cellular aging
• Not associated with organ dysfunction or disease
• Helps distinguish normal aging changes from pathologic pigment deposition (eg, hemosiderin, melanin)

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