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Dermatology path > UVR and skin > Flashcards

UVR and skin Flashcards

How UVL causes cancer; natural defense; acute/chronic effects of UVL; props of UVL

1
Q

UVR wavelengths and damage

A

100-400nm (short) allows DNA damage

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2
Q

What is significant about UVC rays?

A

only 290nm so no atmospheric penetration but most potent of all UVL

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3
Q

What happens when UVC rays are produced artificially then absorbed by DNA?

A

RNA and proteins are damaged and may be unviable leading to lethality of epidermal cells

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4
Q

What waveband is SPF testing done on?

A

UVB (290-320nm)

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5
Q

Can a person inside get UVB rays?

A

no; glass filters it out

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6
Q

What is the most active in producing photochemical reactions in skin?

A

UVB

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7
Q

What is the least potent of all UVR?

A

UVA

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8
Q

What is responsible for photoaging? why?

A

UVA => penetrates deeper than UVB

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9
Q

What are factors that modify UVR at earth?

A

atmosphere; latitude; altitude; surface reflection; cloud; solar flare activity; time of day; season

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10
Q

What blocks most wavelengths below 300nm?

A

ozone: UVC completely blocked; UVB up to 5% remains

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11
Q

Why is skin cancer expected to continue to rise?

A

depletion of ozone layer

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12
Q

Why are you more likely to burn on equivalent days in Texas as compared to vermont?

A

sunlight travels through more atmosphere to reach surface

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13
Q

Who is more likely to burn on a sunny day: person in denver or in San Fransisco?

A

Denver as UVR is increased by 4% every 1000ft increase in altitude

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14
Q

Give order of most likely to burn from UVR: sand, water, snow

A

Snow (most likely) > Sand > water

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15
Q

Why can a person burn on a cloudy day?

A

clouds scatter the UVR but do not absorb it

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16
Q

What are the 3 options that sunlight has when it hits the skin?

A

reflect; absorbed by epidermis and dermis DNA, proteins; penetrates into tissues and dissipates

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17
Q

How is action spectrum determined?

A

UV absorbing properties of molecule that initiates the response: chromophore

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18
Q

What are the major UVB chromophores in skin?

A

DNA; urocanic acid; aromatic amino acids

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19
Q

Acute and chronic responses to UVR depend on what?

A

skin phototype (types I-VI)

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20
Q

What are acute effects of UVR on skin?

A

sunburn; immunomodulation; tan; epidermal hyperplasia; Vit D photosynthesis; DNA damage (apoptosis, cell cycle arrest)

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21
Q

What is the erythema and heat of a sunburn a result of?

A

vasodilation and increased blood flow

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22
Q

Why is pain/pruritus associated with sunburn?

A

release of cytokines

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23
Q

In an acute sunburn, what can be seen histologically?

A

keratinocyte damage; inflammation; intercellular edema; perivascular edema

24
Q

72 hours after a sunburn, what can be seen?

A

hyperkeratosis, acanthosis

25
Q

What is the pathogenesis of a suntan (immediate response)?

A

begins during radiation; oxidation/redistribution of melanin; no protection against UVB

26
Q

What causes a suntan (immediate response)?

A

UVA and visible light

27
Q

What causes the delayed tanning response of a suntan?

A

UVB

28
Q

What is the pathogenesis of a delayed tanning suntan?

A

visible 72hrs later and lasts weeks due to increased melanin synthesis and transfer of melanosomes to keratinocytes to provide photoprotection

29
Q

What are 2 chronic effects of UVR on skin?

A

photaging and photocarcinogenesis

30
Q

What are typical cancers associated with UVR and photocarcinogenesis

A

BCC; squamous cell carcinoma; melanoma

31
Q

What is solar elastosis?

A

result of chronic UV radiation seen on histological slides

32
Q

clinical features of chronologic aging

A

smooth, pale finely wrinkled skin w/ benign growths

33
Q

clinical features of photoaging

A

dry, deeply wrinkled, inelastic leathery, atrophic; telangiectasias; irregular pigmentation; comedone and cyst formation; actinic keratoses; benign growths

34
Q

What are examples of irregular pigmentation associated with photoaging?

A

ephelides (freckles); solar lentigo (age spots); hypopigmentation

35
Q

What are deep wrinkles on the posterior neck?

A

cutis rhomboidalis nuchae

36
Q

What is a poikiloderma

A

reticulate hyperpigmentation; telangiectasia; mild atrophy

37
Q

What UVRs cause photoaging?

A

UVB and UVA

38
Q

Direct damage from UVB occurs via what mechanism?

A

direct absorption of photons by bases of DNA

39
Q

What are DNA photoproducts?

A

dimers formed by covalent binding of 2 adjacent pyrimidines in same polynucleotide chain

40
Q

stratum corneum defense against UVR

A

reflection

41
Q

Melanin defense against UVR

A

melanin

42
Q

tumor suppressor genes against UVR

A

p53; patched; CDKN2A

43
Q

What are intracellular ways of defense against UVR?

A

DNA repair pathways; apoptosis

44
Q

What is xeroderma pigmentosum?

A

heritable disease characterized by marked sensitivity to UV radiation

45
Q

What are patients with XP deficient in?

A

deficient repair of UV induced DNA damage affecting nucleotide excision repair

46
Q

What is the result of most XP patients?

A

high rates of skin cancers at young age with increased risk for other malignancies

47
Q

What are first signs of XP?

A

very early photodamage=> freckles; early wrinkling; skin atrophy

48
Q

When does XP typically present?

A

early childhood w/ marked photosensitivity

49
Q

When does first skin cancer typically present in XP patients?

A

median age of 8

50
Q

Other than skin, what other body locations are affected by XP?

A

CNS (neurologic degen); Eyes (premature agin, dry, corneal scarring, tumors)

51
Q

What and when do most patients with XP die of?

A

32 y/o from metastatic skin cancer and neurologic degeneration

52
Q

How does UVR cause immunosuppression?

A

local and systemic effects => sun exposure causes Langerhans to disappear from skin in mild sunburn due to DNA damage

53
Q

When is UV light considered for Tx?

A

skin diseases caused or enhanced by lymphs or Langerhans => psoriasis; cutaneous lymphoma; eczema

54
Q

What is significant about UVA suntans?

A

provide 10x less protection against sunburn than UVB

55
Q

What skin diseases are strongly associated with tanning beds?

A

melanoma; non melanoma skin cancers

56
Q

T/F Risk of skin cancer increases by 75% in ppl who use tanning beds

A

true

57
Q

What is Favre-Racouchot syndrome?

A

skin disease in sun damaged individuals characterized by yellowish thickening of skin w/ nodules, comedones and follicular cysts

Dermatology path (11 decks)

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