UVR and skin

Question 1

UVR wavelengths and damage

Answer 1

100-400nm (short) allows DNA damage

Question 2

What is significant about UVC rays?

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What waveband is SPF testing done on?

Answer 4

UVB (290-320nm)

Question 5

Can a person inside get UVB rays?

Answer 5

no; glass filters it out

Question 6

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

Answer 6

UVB

Question 7

What is the least potent of all UVR?

Answer 7

UVA

Question 8

What is responsible for photoaging? why?

Answer 8

UVA => penetrates deeper than UVB

Question 9

What are factors that modify UVR at earth?

Answer 9

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

Question 10

What blocks most wavelengths below 300nm?

Answer 10

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

Question 11

Why is skin cancer expected to continue to rise?

Answer 11

depletion of ozone layer

Question 12

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

Answer 12

sunlight travels through more atmosphere to reach surface

Question 13

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

Answer 13

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

Question 14

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

Answer 14

Snow (most likely) > Sand > water

Question 15

Why can a person burn on a cloudy day?

Answer 15

clouds scatter the UVR but do not absorb it

Question 16

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

Answer 16

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

Question 17

How is action spectrum determined?

Answer 17

UV absorbing properties of molecule that initiates the response: chromophore

Question 18

What are the major UVB chromophores in skin?

Answer 18

DNA; urocanic acid; aromatic amino acids

Question 19

Acute and chronic responses to UVR depend on what?

Answer 19

skin phototype (types I-VI)

Question 20

What are acute effects of UVR on skin?

Answer 20

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

Question 21

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

Answer 21

vasodilation and increased blood flow

Question 22

Why is pain/pruritus associated with sunburn?

Answer 22

release of cytokines

Question 23

In an acute sunburn, what can be seen histologically?

Answer 23

keratinocyte damage; inflammation; intercellular edema; perivascular edema

Question 24

72 hours after a sunburn, what can be seen?

Answer 24

hyperkeratosis, acanthosis

Question 25

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

Answer 25

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

Question 26

What causes a suntan (immediate response)?

Answer 26

UVA and visible light

Question 27

What causes the delayed tanning response of a suntan?

Answer 27

UVB

Question 28

What is the pathogenesis of a delayed tanning suntan?

Answer 28

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

Question 29

What are 2 chronic effects of UVR on skin?

Answer 29

photaging and photocarcinogenesis

Question 30

What are typical cancers associated with UVR and photocarcinogenesis

Answer 30

BCC; squamous cell carcinoma; melanoma

Question 31

What is solar elastosis?

Answer 31

result of chronic UV radiation seen on histological slides

Question 32

clinical features of chronologic aging

Answer 32

smooth, pale finely wrinkled skin w/ benign growths

Question 33

clinical features of photoaging

Answer 33

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

Question 34

What are examples of irregular pigmentation associated with photoaging?

Answer 34

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

Question 35

What are deep wrinkles on the posterior neck?

Answer 35

cutis rhomboidalis nuchae

Question 36

What is a poikiloderma

Answer 36

reticulate hyperpigmentation; telangiectasia; mild atrophy

Question 37

What UVRs cause photoaging?

Answer 37

UVB and UVA

Question 38

Direct damage from UVB occurs via what mechanism?

Answer 38

direct absorption of photons by bases of DNA

Question 39

What are DNA photoproducts?

Answer 39

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

Question 40

stratum corneum defense against UVR

Answer 40

reflection

Question 41

Melanin defense against UVR

Answer 41

melanin

Question 42

tumor suppressor genes against UVR

Answer 42

p53; patched; CDKN2A

Question 43

What are intracellular ways of defense against UVR?

Answer 43

DNA repair pathways; apoptosis

Question 44

What is xeroderma pigmentosum?

Answer 44

heritable disease characterized by marked sensitivity to UV radiation

Question 45

What are patients with XP deficient in?

Answer 45

deficient repair of UV induced DNA damage affecting nucleotide excision repair

Question 46

What is the result of most XP patients?

Answer 46

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

Question 47

What are first signs of XP?

Answer 47

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

Question 48

When does XP typically present?

Answer 48

early childhood w/ marked photosensitivity

Question 49

When does first skin cancer typically present in XP patients?

Answer 49

median age of 8

Question 50

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

Answer 50

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

Question 51

What and when do most patients with XP die of?

Answer 51

32 y/o from metastatic skin cancer and neurologic degeneration

Question 52

How does UVR cause immunosuppression?

Answer 52

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

Question 53

When is UV light considered for Tx?

Answer 53

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

Question 54

What is significant about UVA suntans?

Answer 54

provide 10x less protection against sunburn than UVB

Question 55

What skin diseases are strongly associated with tanning beds?

Answer 55

melanoma; non melanoma skin cancers

Question 56

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

Answer 56

true

Question 57

What is Favre-Racouchot syndrome?

Answer 57

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