Cell Injury-2: Fatty Change and Pigment Disorders

Study Notes

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.

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.

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.

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.

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.

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).