[C] 1.35 Pathologic pigmentation caused by melanin, lipofuscin, and ceroid

Question 1

Melanin, lipofuscin and ceroid are grouped as…

Answer 1

Autochton pigments

Anhaemoglobinogenous pigments

Question 2

Melanin: Chemistry

Answer 2

• Insoluble in water, acids and fat solvents
• Soluble in K-OH, Na-OH & H₂O₂ (Bleach)

Question 3

Melanin is produced by

Answer 3

Ectodermal origin cells:

• Synthesis initiation by tyrosinase enzymes
• MSH stimulates production of:
  
  • Melanin
  • Brown-black pigment (no iron)

Question 4

Give the order of melanocyte production of melanin granules

Answer 4

1. Premelanosoma
2. Melanosoma I
3. Melanosoma II
4. Melanin granule

Enzyme: Tyrosinase

Question 5

Where is melanin stored?

Answer 5

Melanophages

Question 6

Reaction of formin melanin

Answer 6

Tyrosin → Melanin

• Tyrosinase enzyme (oxidation)
• Stimulation by the hypophysis (MSH & ACTH)

Question 7

Where in the body is melanin located (physiologically)

Answer 7

• Skin
  
  • Epidermis & corium
• During prengnancy
  
  • Nipples, face, mid-line of belly
• Eye
• Ganglion cells
• Leptomenings
• Oral cavity
• Mammary gland - Berkshire pigs
• Serous membrane - Reptiles & birds

Question 8

Give the three variations of abnormal pigmentation

Answer 8

1. Hyperpigmentatio
2. Hypopigmentatio
3. Albinismus

Question 9

Hyperpigmentatio

Answer 9

• Radiation & arsenic treatment
• Naevi (naevus pigmentosus) (birth mark)
• Focal melanosis
• Melanoma
• Acanthosis nigricans
• Addision’s disease

Question 10

Hypopigmentatio

Answer 10

• Leukoderma (surgical treatment)
• Vitiligo (pigment free area)

Question 11

Acanthosis nigricans

Answer 11

• Unknown origin
• Hyperpigmentation of axilla, thorax, inguinal or circum-anal region
• Uneven proliferation of epithelial cells in stratum spinosum
• Thickened skin with uneven surface
• Velvet touch

Question 12

Hypopigmentation

Answer 12

• Age
• Vitiligo (hamartia) (Depigmentation of skin)
• Leukoderma (Focal absence after injury)
• Trophoneurotic problems
  
  • Dourine in horses
  • Depigmented areas
• Pale areas after maceration
• Albinism
  
  • Pathological absence of melanin
  • Congenital in rodents

Question 13

Lipofuscin

Answer 13

Golden-brown pigment - Proteins & lipids, no iron

• Formed in lysosomes of ageing cells

Question 14

Lipofuscin production

Answer 14

Autooxidation of unsaturated lipids

• All three germ layers may contain insoluble in water, acid & alkali

Question 15

Lipofuscin: Location

Answer 15

• Liver
• Kidney tubule
• Adrenal gland
• Choroid plexus
• Muscle cells

Question 16

Observations of lipofuscin under the electron microscope

Answer 16

• Dense
• Amorphous autophagosomes
• Granules
• Lipids

Question 17

Lipofuscin: Pathogenic conditions

Answer 17

• Brown bowel syndrome
• Neuronal ceroid lipofuscinosis

Question 18

Brown bowel syndrome

Answer 18

• Dogs
• Diarrhoeal diseases
• Steatorrhea (High fat excretion)
• Pancreatic acinar deficiency
• Malabsorption
• Intestine: Brown
  
  • Smooth muscle cells

Question 19

Neuronal ceroid lipofuscinosis

Answer 19

English setter, cattle, sheep, cat

• IC accumulation
• The progressive loss of cells in the brain and the cerebral function

Question 20

Ceroid

Answer 20

• Lipogenous pigment
• Partially oxidised & polymerised unsaturated fatty acid bound to proteins
• Produced in macrophages and hepatocytes
• Ziehl-Neelsen positive

Yellow fat disease

Question 21

Yellow fat disease

Answer 21

Alcohol soluble - icterus

Question 22

Ceroid-like pigment

Answer 22

Yellow appearance

• Lipocytes
• Macrophages
• MPS-cells
• Yellow adipose
  
  • Yellow fat disease
  • Caused by high unsaturated FA in feed

Question 23

Ochronosis

Answer 23

(Alkaptonuria)

• Inherited disturbance of the protein metabolism
• Aa → Homogentisic-acid
• Oxidation → Coloured substance

Question 24

Ochronosis signs

Answer 24

Cartilage, tendons & ligaments become greenish

Bones don’t become discoloured