Cell Injury-2: Fatty Change and Pigment Disorders

Cell Injury-2

• Intended Learning Objectives:
  • Describe the definition, causes, sites, significance, and morphologic changes of fatty change.
  • List the types and causes of pigment disorders.
  • Recall the definition and types of pathologic calcification.

Fatty Change

• Definition: Abnormal accumulation of triglycerides within parenchymal cells.
• Site:
  • Liver: The most common site, with a central role in fat metabolism. It can also occur in the heart due to conditions like anemia or starvation (anorexia nervosa).
  • Other sites: Skeletal muscle, kidney, and other organs.
• Causes:
  • Toxins (most importantly, alcohol abuse)
  • Diabetes mellitus
  • Protein malnutrition (starvation)
  • Obesity
  • Hypoxia
• Significance: Depends on the severity of the accumulation.
  • Mild: May have no effect.
  • Severe: Fatty change can lead to steatohepatitis and cirrhosis.

Morphological Features of Fatty Liver (Grossly)

• Size: Enlarged
• Shape: Preserved
• Surface: Smooth
• Color: Yellowish
• Consistency: Soft and greasy
• Capsule: Stretched (non-adherent)
• Cross-section (C/S): Bulges out with rounded edges

Morphological Features of Fatty Liver (Microscopically)

• Cells: Swollen, cytoplasm containing fat droplets.
• Fat: Appears as empty vacuoles in H&E stained sections, but stained in frozen sections by fat stains, like Oil Red O.

Pigment Disorders

• Melanin Deficiency

  • Albinism: Hereditary absence of tyrosinase enzyme, leading to white hair, skin, iris, and choroids.
  • Leucoderma: White skin patches due to melanin loss; includes vitiligo, secondary to leprosy or syphilis, and idiopathic.

• Melanin Hyperpigmentation

  • Prolonged sun exposure.
  • Chloasma (melasma): Brown patches on the face (especially around the nipple and genitalia) that occurs due to increased estrogen levels.
  • Freckles: Brown spots due to exposure to ultraviolet rays, with a genetic predisposition.

• Lipochrome (lipofuscin):

  • Yellowish-brown pigment, normally found in the heart, liver, testes, seminal vesicles, and adrenals.
  • Increases with age and in atrophic conditions like brown atrophy of the heart.

• Hemoglobin-derived pigments:

  • Bilirubin: Elevated levels can result in jaundice.
  • Hemosiderin: Increased in conditions like hemosiderosis and certain parasitic infections. It stains positively with Prussian blue.
  • Hemoglobin (haematin): Increased levels occur in malaria and bilharziasis.

Exogenous Pigmentations

• Tattooing: Indian ink pigments are permanently deposited by being trapped by dermal macrophages.
• Anthracosis: Deposits of carbon dust in the lungs, from inhalation, which are phagocytosed by alveolar macrophages.

Pathologic Calcification

• Definition: Abnormal deposition of calcium salts in tissues, not in bone or teeth.
• Dystrophic Calcification: Calcification in dead or dying tissues (e.g., necrotic areas, atheromatous plaques). Occurs with normal serum calcium levels.
• Metastatic Calcification: Abnormal calcium deposition in normal tissues, usually associated with hypercalcemia (elevated blood calcium).