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AMP FPP > Intracellular Accumulation nd Pigments > Flashcards

Intracellular Accumulation nd Pigments Flashcards

1
Q

What is intracellular accumulation

A

These are substances which accumulate in the cell due to increased production or defective removal by the cell.

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2
Q

What are the types of accumulations in intracellular accumulation

A

These accumulations could be endogenous/exogenous (source), toxic/non-toxic (effect), temporary/permanent (residency) and may be found in the cytoplasm or nucleus (location).

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3
Q

What are the causes of intracellular accumulation

A
  1. A normal endogenous substance produced at a normal or increased rate but the rate of metabolism is inadequate to remove it. E.g. is seen with fatty droplets in the liver.
  2. A normal endogenous substance accumulates due to a defect in the enzyme required for its metabolism. E.g. Lysosomal storage dx
  3. An abnormal endogenous substance accumulates e.g. the product of a mutated gene or misfolded proteins which cannot be degraded accumulate in the cell. E.g. neuro degenerative diseases
  4. An abnormal exogenous substance accumulates in the cell because the cell lacks the ability to degrade it or transport it to other sites. E.g. is carbon particles in alveolar macrophages.
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4
Q

What is Steatosis

A

Fatty change

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5
Q

Where can steatosis be found

A

• Mostly seen in the liver because it is the major organ involved in fat metabolism. May also be present in the heart, muscle and kidney

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6
Q

What are the causes of steatosis

A

Alcohol abuse, diabetes and obesity. Alcohol alters mitochondrial and microsomal function leading to increased synthesis and reduced breakdown of lipids. In DM, elevated glucose provides more substrate for triglyceride synthesis.

Carbon tetrachloride (CCl4) and protein malnutrition. cause reduced apoprotein synthesis which results in defective lipid transport

Hypoxia impairs fatty acid oxidation

Starvation causes mobilization of fat from peripheral stores

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7
Q

What special stains are used to identify fatty droplets microscopically

A

Special stains like Sudan black & Oil Red-O

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8
Q

Give 4 examples of cholesterol accumulation

A

• Atherosclerosis in blood vessels
• Xanthomas in connective tissue and skin
• Cholesterolosis in the gall bladder
• Niemann-Pick disease type C

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9
Q

Examples of protein intracellular accumulation

A
  1. In proteinuria, droplets in proximal renal tubules
  2. Immunoglobulins may accumulate in plasma cells within the ER producing inclusions called Russell bodies
  3. Alpha 1 antitrypsin deficiency (emphysema), the enzyme is deficient because its precursors are misfolded and have accumulated in the liver.
  4. Accumulation of cytoskeletal proteins: keratin intermediate filaments are seen in alcoholic hyaline which is characteristic of alcoholic liver disease. Neurofibrillary tangles found in Alzheimer disease are made up of neurofilaments
  5. Aggregation of abnormal proteins e.g. in amyloidos
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10
Q

Examples of glycogen cell accumulation

A

• Seen in disorders of glucose or glycogen metabolism. E.g. in D.M, normal glucose uptake by cells is impaired. Seen in hepatocytes (stained by PAS/PASD)
• Also seen in genetic disorders of enzymes involved in glucose/glycogen metabolism. These are called glycogen storage diseases

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11
Q

What are the types of pigments

A

Exogenous and Endogenous
Normal e.g. melanin or abnormal e.g. tatoo

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12
Q

Examples of exogenous pigments

A

• Carbon (coal dust): most common, results in anthracosis, coal workers pneumoconiosis
• Tattoos

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13
Q

Examples of endogenous pigments

A

• Lipofuscin: wear and tear pigment
• Hemosiderin: Old haemorrhage, Fe overload (hemosiderosis). From
ferritin micelles
• Melanin

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14
Q

What are the 5 types of intermediate filaments

A

Keratin filaments (skin)
Glial filaments (astrocytes)
Desmin filaments (muscles)
Neuro filaments (neurons)
Vimentin filaments (connective tissue)

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15
Q

What absorb tattoo pigments

A

Dermal macrophages

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16
Q

What causes difficulty in respiration in anthracosis

A

the macrophages which ingest the inhaled carbon particles, also elaborate cytokines which encourage the formation of fibrosis in the lungs

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17
Q

What pigment is ubiquitous and is inhaled daily as an air pollutant

A

Carbon (coal dust)

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18
Q

When carbon is phagocytosed by macrophages in the alveoli, what happens

A

The macrophages transport them via lymphatic channels to the regional lymph nodes

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19
Q

What is pneumoconiosis

A

A disease condition where there is a fibroblastic reaction to the large amounts of coal dust inhaled by workers in this profession.

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20
Q

What does simple coal workers pneumoconiosis progress to

A

Progressive massive fibrosis
(Complicated pneumoconiosis)

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21
Q

What are the endogenous pigments (list out)

A

• Lipofuscin (wear and tear
pigment)
• Hemosiderin
• Homogentisic acid – deposited in the connective tissues, skin in patients with alkaptonuria. The pigmentation is known as ochronosis.
• Melanin
• Bilirubin

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22
Q

What does Lipoduscin consist of

A

Granules composed of lipid-protein complexes.

23
Q

Where can lipofuscin be found

A

•Found in ageing or debilitating diseases and are the end
products of oxygen radical mediated membrane damage
which are not eliminated by intracellular lipid peroxidation.
● They subsequently persist in the lysosomes as collections of
indigestible material

24
Q

What’s the morphology of lipofuscin

A

● Yellow-brown, finely granular cytoplasmic (perinuclear) pigment.
● No gross features

25
Q

What is melanin

A

Non-haemoglobin derived brown-black pigment.

26
Q

Where can melanin be found

A

skin, hair

27
Q

How is melanin synthesized

A

Synthesized in the melanocytes and dendritic cells by the
action of tyrosinase on tyrosine to form dihydroxyphenylalanine (DHPA).

28
Q

Disorders of melanin pigmentation

A

generalised and localised hyperpigmentation/hypopigmentation

29
Q

Examples of generalised hyperpigmentation

A

● Addison’s disease: hyperpigmentation of sun exposed areas
● Chloasma: seen in pregnancy/oral contraceptive pills.
Oestrogen induced hyperpigmentation of the face, nipples,genitalia.
● Chronic arsenic poisoining: classic raindrop pigmentation of
the skin.

30
Q

Examples of focal hyperpigmentation

A

● Neurofibromatosis: Cafe-au-lait spots
● Peutz-Jeghers syndrome: Peri-oral
● Melanosis coli: mucosa of the colon
● Melanotic tumours: skin
● Lentigo: skin
● Dermatopathic lymphadenopathy: Lymph nodes draining
skin lesions

31
Q

What is defective in generalized hypopigmentation (albinism)

A

Tyrosinase

32
Q

Which general hypopigmentation cases have almost no pigment in the skin and hair and complain of severe photophobia.

A

Oculocutaneous cases of albinism

33
Q

What can occur from chronic sun exposure of an albino

A

Skin cancer

34
Q

Examples of focal hypopigmentation

A

● Leucoderma: localised loss of skin pigmentation. Autoimmune condition.
● Vitiligo: More common type, may be familial
● Acquired focal hypopigmentation: healing of wounds,
leprosy, lupus etc.

35
Q

What is alkaptunuria (4 characteristics)

A

● Autosomal recessive disorder
● Deficiency of oxidase enzyme which is required to break
down homogentisic acid.
● Homogentisic acid therefore accumulates in the tissues
and is excreted in the urine.
● Urine turns black if allowed to stand for a few hours in the
air (oxidation of homogentisic acid).

36
Q

What’s the black pigment in alkaptunuria called and where is it deposited

A

Called ochronosis and is deposited both inter and intracellularly. E.g. Joints, ligaments, skin tissue.

37
Q

Iron in tissues are stored as what

A

○ Ferettin (Fe complexed to apoferritin)
○ Haemosiderin (formed by aggregates of ferritin)

38
Q

When does excessive accumulation of heamosiderin occur

A

Excessive storage of haemosiderin occurs when there is increased breakdown of red blood cells or systemic iron overload

39
Q

What are the types of heamosiderin accumulation

A

localised or generalised

40
Q

What happens in localised haemosiderosis

A

● When there is haemorrhage into the tissue, the red blood cells are lysed releasing their haemoglobin which is then taken up by macrophages, degraded and stored as haemosiderin

41
Q

Examples of localized haemosiderosis

A

○ Haemosiderin laden macrophages at sites of endometriotic deposits
○ Haemosiderin laden alveolar macrophages (heart failure cells) in the lungs in left ventricular failure

42
Q

What are 3 causes of generalized haemosiderosis

A

● Increased breakdown of haemoglobin e.g. chronic hemolytic anaemia, excessive blood transfusion
● Excessive intestinal absorption of iron
● Excessive iron intake e.g. multivitamins, alcohol brewed in
certain vessels.

43
Q

What is Excessive absorption of iron even with normal intake known as

A

idiopathic or hereditary haemochromatosis.

Autosomal dominant disease

44
Q

What does Treatment with blood transfusions or parenteral iron do to hemolytic anemia

A

Worsens the haemosiderosis

45
Q

What are the symptoms of idiopathic/hereditary haemochromatosis

A

○ Pigmented liver cirrhosis
○ Skin pigmentation
○ Pancreatic damage resulting in diabetes (‘bronze
diabetes’)

46
Q

Where was excessive iron intake first observed

A

Bantu tribe of South Africa.
Due to Consumption of alcohol brewed in ungalvanised iron
vessels.

47
Q

What was identified as the predisposing factor to this overload of iron intake

A

A gene called ferroportin

48
Q

Describe the histology of haemosiderosis

A

● Intracytoplasmic coarse, golden-brown, granular pigment
● Visualised with Prussian blue/Perl’s stain

49
Q

What stain is used to identify haemosiderin

A

Prussian blue/Perl’s stain

50
Q

What is bilirubin

A

Pigment also derived from haemoglobin but is non-iron containing, found in bile.

51
Q

What does hyperbilirubinemia cause

A

Jaundice

52
Q

What’s the aetiology of hyperbilirubinemia

A

○ Increased production (excessive RBC destruction)
○ Defective conjugation (liver disease/injury)
○ Defective transport (intra/extrahepatic bile ducts)

53
Q

How does bilirubin accumulate in the body

A

Accumulates as yellow pigment in the fluids and tissues of the body e.g. hepatocytes, skin, sclera.

54
Q

What does high level of unconjugated bilirubin cause in infants

A

In infants, high levels of unconjugated bilirubin may cause brain injury (kernicterus)

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