UV and the skin

Question 1

which ray causes most skin damage?

Answer 1

UVB

Question 2

what is the main source of vitamin D?

Answer 2

UVB light

Question 3

where is vitamin D metabolised?

Answer 3

liver

Question 4

where is vitamin D distributed to?

Answer 4

bones and gut

Question 5

who is most at risk of vit D deficiency?

Answer 5

photoprotection
photosensitivity diseases and skin cancer
higher skin phototypes

Question 6

what bone disorders can vitamin D lead to in children and adults?

Answer 6

Rickett’s
osteoporosis

Question 7

what is the therapeutic uses of UVR?

Answer 7

psoriasis and eczema

Question 8

what rays does phototherapy use?

Answer 8

UVB

Question 9

what rays does photochemotherapy use?

Answer 9

psoralen + UVA = PUVA

Question 10

what is photodynamic therapy used for?

Answer 10

superficial non-melanoma SC and pre-cancer

Question 11

what are the diagnostic uses of UVR and visible light?

Answer 11

drug photosensitivity
solar urticaria
investigates and diagnoses photosensitivity diseases

Question 12

what are the risks of UVR exposure?

Answer 12

sunburn
eyes damage
photoaging
skin cancer
photosensitivity diseases

Question 13

what do the classes of fitzpatrick skin phototypes depend on?

Answer 13

eumelanin:pheomelanin ratio

Question 14

what are the Fitzpatrick skin phenotypes?

Answer 14

I - burns
II - burns, can tan
III - tans, can burn
IV - tans
V - dark brown skin
VI- black skin

Question 15

what rays do sunbeds use?

Answer 15

UVA

Question 16

what are the cutaneous effects of UVR?

Answer 16

DNA damage and signature mutations
immunosuppression
induction of oncogenes and tumour suppressor genes

Question 17

what is the most commonest skin cancer in light skin populations?

Answer 17

basal cell carcinoma

Question 18

what are the mutations that UVB causes?

Answer 18

a photon of UVR is absorbed by DNA in nucleus of keratinocyte
formation of pyrimidine dimers and distortion of helix

Question 19

how does UVA induce photocarcinogenesis?

Answer 19

indirect oxidative DNA damage, penetrates more deeply into skin than UVB

Question 20

how does UVB induce photocarcinogenesis?

Answer 20

direct DNA damage, 1000 times more damaging than UVA when sun is directly overhead

Question 21

how do oncogenes cause cancer?

Answer 21

permanently activated
lead to uncontrolled cell growth and proliferation

Question 22

how do tumour suppressors cause cancer?

Answer 22

failed normal apoptotic response to UV
uncontrolled cell growth and proliferation

Question 23

what gene has the role of preventing damage to DNA?

Answer 23

p53 tumour suppressor genes

Question 24

how do basal cell carcinomas occur?

Answer 24

inactivation mutation of PTCH gene which activates hedgehog signalling

Question 25

what are UVR-induced pyrimidine dimers removed by?

Answer 25

nucleotide excision repair (NER) pathway

Question 26

what is the NER pathway?

Answer 26

DNA repair mechanism

Question 27

what can a deficiency in NER cause?

Answer 27

xeroderma pigmentosum

Question 28

what causes immunosuppression?

Answer 28

Langerhan's cell migration suppression of delayed hypersensitivity

Question 29

what is the Wilkinson's triad?

Answer 29

sparing of upper eyelids, periorbital areas, lower lip, under chin, nose and spectacles

Question 30

what is polymorphic light eruption (PLE)?

Answer 30

recurrent abnormal reaction to sunlight or artificial radiation type IV hypersensitivity resistant Langerhan's cells

Question 31

what are the immunological photodermatoses?

Answer 31

actinic prurigo chronic actinic dermatitis solar urticaria

Question 32

what types of reactions are actinic prurigo and chronic actinic dermatitis?

Answer 32

delayed cell mediated type IV hypersensitivities

Question 33

what type of reaction is solar urticaria?

Answer 33

immediate type I IgE mediated

Question 34

which drugs may cause photosensitivities?

Answer 34

thiazide chlorpromazine doxycycline quinine amiodarone

Question 35

what are photoaggrevated diseases?

Answer 35

lupus psoriasis

Question 36

what is xeroderma pigmentosum?

Answer 36

autosomal recessive genetic photodermatosis failure of DNA nucleotide excision repair rapid photoageing of skin and skin cancer

Question 37

which sunscreen chemicals absorb light?

Answer 37

oxybenzone

Question 38

which sunscreen chemicals reflect light?

Answer 38

titanium dioxide