Accumulations and Deposits

Accumulations and Deposits - Cellular Stash Secrets

• Intracellular accumulation occurs via: abnormal metabolism, defective protein folding/transport, enzyme deficiency, or ingestion of indigestible materials.
• Key Examples:
  • Lipids: Steatosis (e.g., fatty liver), cholesterolosis.
  • Proteins: Russell bodies (plasma cells), Mallory-Denk bodies (liver disease).
  • Glycogen: Diabetes mellitus, glycogen storage diseases (GSDs).
  • Pigments: Lipofuscin (wear & tear), melanin, hemosiderin (iron).
  • Calcium: Dystrophic (damaged tissue), metastatic (hypercalcemia).

⭐ Lipofuscin, the "wear-and-tear" pigment, is an insoluble brownish-yellow granular material accumulating in aging cells, particularly heart, liver, and brain.

Accumulations and Deposits - Fat, Protein Pile-Up

• Fatty Change (Steatosis): Abnormal triglyceride accumulation in cells; often reversible.
  • Liver: Most common. Causes: Alcohol, toxins, DM, obesity, malnutrition.
    • Gross: ↑Size, yellow, greasy.
    • Micro: Fat vacuoles (can cause signet ring appearance). Stains: Oil Red O, Sudan Black B (frozen).
  • Heart: "Tigeroid" pattern (severe anemia, diphtheria).
• Protein Accumulation: Excess synthesis/uptake or defective folding/transport; often eosinophilic.
  • Examples:
    • Reabsorption droplets: Renal tubules (proteinuria).
    • Russell bodies: Ig in plasma cell RER (distended).
    • Mallory-Denk bodies: Cytokeratin in hepatocytes (alcoholic liver disease, NAFLD).
    • Neurofibrillary tangles: Alzheimer's (tau protein).
    • $\alpha$1-antitrypsin deficiency: Misfolded protein in liver ER.

  ⭐ Mallory-Denk bodies: Eosinophilic cytokeratin inclusions in hepatocytes (alcoholic hepatitis, NAFLD), appear as rope-like structures.

Accumulations and Deposits - Sugar & Stain Stories

• Glycogen:
  • Excess intracellular glucose.
  • Causes: Diabetes (DM), Glycogen Storage Diseases (GSDs).
  • Sites: Liver, kidney (Armanni-Ebstein lesions in DM), heart.
  • Stain: PAS (+, magenta), diastase-sensitive.
  • Appearance: Clear cytoplasmic vacuoles.
• Pigments (Endogenous):
  • Lipofuscin (Wear & Tear):
    • Yellow-brown granules; lipid peroxidation.
    • Sites: Heart, liver, brain (elderly).
    • Stain: Sudan Black B.
  • Melanin:
    • Brown-black; tyrosine oxidation.
    • Cells: Melanocytes.
    • Stain: Fontana-Masson (silver).
  • Hemosiderin (Iron):
    • Golden-yellow/brown; hemoglobin breakdown (ferritin aggregates).
    • Sites: Hemorrhage, chronic congestion.
    • Stain: Prussian blue (Perls') - iron blue.

    ⭐ Hemosiderin-laden macrophages in alveoli are "heart failure cells" (chronic pulmonary congestion).

  • Bilirubin (No Iron):
    • Yellow-green/brown; heme degradation.
    • Sites: Liver (jaundice, cholestasis).
    • Stain: Hall's (Fouchet) - bilirubin green.

Accumulations and Deposits - Outside Cell Overload

• Amyloidosis: Extracellular deposition of misfolded fibrillar proteins (β-pleated sheets).

  • Stain: Congo Red → apple-green birefringence (polarized light).
  • Key Types:
    • AL: Ig light chains (plasma cell dyscrasias).
    • AA: Serum Amyloid A (chronic inflammation).
    • Aβ: APP (Alzheimer's disease plaques).
    • ATTR: Transthyretin (senile/familial amyloidosis).
  • Organs: Kidney (nephrotic syndrome), heart (restrictive cardiomyopathy), liver, spleen.

  ⭐ Congo Red stain showing apple-green birefringence under polarized light is pathognomonic for amyloidosis.

• Pathologic Calcification: Abnormal Ca²⁺ salt deposition. Two types:

• Gout: Monosodium Urate (MSU) crystal deposition in/around joints; from hyperuricemia.
  • Crystals: Needle-shaped, negatively birefringent. 📌 Mnemonic: Yellow when Parallel (YAP), Blue when Perpendicular (BUP) to compensator.
  • Tophus: Pathognomonic; MSU crystals + chronic granulomatous inflammation (macrophages, giant cells).

High‑Yield Points - ⚡ Biggest Takeaways

• Steatosis: Reversible triglyceride accumulation, common in the liver.
• Cholesterol: Accumulates in atherosclerosis, xanthomas, and cholesterolosis.
• Lipofuscin: "Wear-and-tear" pigment from lipid peroxidation, linked to brown atrophy.
• Hemosiderin: Iron-storage pigment, Prussian blue positive, indicates hemorrhage or iron overload.
• Pathologic Calcification: Dystrophic in damaged tissue (normocalcemia); Metastatic with hypercalcemia.
• Amyloidosis: Extracellular misfolded proteins; Congo Red stain shows apple-green birefringence.
• Proteinopathies: Include Russell bodies (immunoglobulins) and Mallory-Denk bodies (cytokeratin).