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Dermatology > Photocarcinogenesis > Flashcards

Photocarcinogenesis Flashcards

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Dermatology Board Prep flashcards
1
Q

What is xeroderma pigmentosum?

A

Genetic condition which reduces the ability of the body to repair DNA damage causing a 2000 fold increase in skin cancer

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2
Q

Which type of skin cancers are found on chronically sun exposed sites?

A

Squamous cell carcinomas

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3
Q

Which factors are most likely to cause the development of melanomas or BCCs?

A
  1. Sunburn
  2. Intense intermittent or recreational UV exposure
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4
Q

Artificial UV (sunbeds) shows the greatest increase in which type of cancer?

A

Squamous cell carcinoma

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5
Q

What are the two major types of UVB induced DNA lesion?

A
  1. Cyclobutane pyrimidine dimers
  2. Pyrimidine-pyrimidine (6-4)
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6
Q

How is the rate of cancer development impacted by the use of TNFa inhibitor usage in conditions such as psoriasis?

A

Increases

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7
Q

How is UVA induced DNA damage repaired?

A

Base excision repair

(Base-free deoxyribose is cleaved away by endonuclease)

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8
Q

Which type(s) of skin cancer have increased incidence after exposure to certain chemicals such as coal tar pitch, soot, arsenic, shale oils etc. ?

A
  1. Basal cell carcinoma
  2. Squamous cell carcinoma

(Only non-melanoma skin cancers)

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9
Q

Which enzyme is responsible for excising oxidised bases from UVA damage?

A

DNA glycosylase

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10
Q

Which band of UV radiation directly causes DNA damage?

A

UVB

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11
Q

Which band of UV radiation penetrates deepest into the skin?

A

UVA

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12
Q

Mutations in PTCH1 are associated with which type of skin cancer?

A

Basal cell carcinoma

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13
Q

Why are fair skinned people at higher risk of developing melanoma?

A

More pheomelanin is produced versus eumalanin

Does not protect as well against UV

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14
Q

How is UVB induced DNA damage repaired?

A

Nucleotide excision repair

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15
Q

What is Ras?

A

Growth factor

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16
Q

Which gastro-intestinal condition has a strong association with malignant melanoma?

A

Crohn’s disease

(much higher than UC)

17
Q

Pyridine dimers are formed due to exposure to which UV band?

A

UVB

18
Q

Most skin cancers are of which class?

A

Non-melanoma skin cancers

19
Q

What is a proto-oncogene?

A

Normal form of an oncogene

(not yet mutated)

20
Q

UVB induced DNA damage is repaired via which method?

A

Nucleotide excision repair

21
Q

UVA induced DNA damage is repaired via which method?

A

Base excision repair

22
Q

How do oncogenes function normally?

A

Cell division will be produced only in response to growth factors (i.e. when growth is required)

23
Q

TNF alpha inhibitor use has been shown to do what?

A

Increase the rate of cancer development

24
Q

Which enzyme cleaves away a base free deoxyribose after UVA induced DNA damage?

A

Endonuclease

(DNA glycosylase cleaves the altered base first)

25
Q

Mutations in Ras/Raf/MAPK are associated with which type of skin cancer?

A

Melanoma

26
Q

How do pyrimidine dimers occur?

A

Bonding between base pairings is disrupted

Some bases bond to adjacent bases on the same DNA strand

27
Q

Describe the steps taken in UVB induced DNA lesion repair

A
  1. Recognition of damaged DNA
  2. Cleavage of damaged DNA on either side of the photoproduct
  3. DNA polymerase fills the gap using the undamaged strand as a template
  4. DNA ligase seals the ends
28
Q

Which comorbidity is most associated with melan oma?

A

Crohn’s disease

(UC is too but to a far lesser degree)

29
Q

How does UVA cause DNA damage?

A

Oxidation of bases

30
Q

In which 3 ways can UV cause immunosuppression?

A
  1. Depletion of Langerhans cells (reduced antigen presentating capability)
  2. Generation of UV induced regulatory T cells
  3. Secretion of anti-inflammaotry cytokines by macrophages and keratinocytes
31
Q

Which two genes are associated with familial melanoma?

A

CDKN2A and CDK4

Dermatology (18 decks)

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