Derm - 2-22 - Photobiology

Front 1

Energy relation to wavelength and freq

Back 1

Inv prop to wl and directly prop to freq.

So with high wavelengths, there is more depth of skin penetration and less energy per photon.

Front 2

Sun transmits...

Back 2

UV radiation, visible light and IR radiations. (going from lowest to highest wavelengths)

Front 3

UVC

Back 3

200-290nm
Mutagenic and carcinogenic but most is absorbed by ozone.

Germicidal activity and welder's have high exposure.

Front 4

UVB

Back 4

290-315nm

About 5% of sun's UVRadiation.

Main cause of sunburn and skin CA.

Much much more tumorigenic and erythmogenic than UVA.

***B = BURN

Front 5

UVA

Back 5

315-400nm

Causes some skin CA, tanning, immune supp, photoaging.

not filtered by glass.

***A=aging

This one goes the deepest in the skin.

Front 6

Sunburn

Back 6

erythema causes it

Does not include the init redness from UVA which is just vasodilation of BVs.

it is UVB induced 6-24 hours after sun exp.

DNA is the chromophore for UVB in keratinocytes which leads to the cell death and mild inflammation.

Front 7

Suntan

Back 7

Immed pigment darkening due to oxidation and redist of existing melanin to top of melanocytes to protect them from damage. This part is due to UVA

UVB induces a tan 3 days later due to more melanocytes, more melanin synth, more transfer of melanosomes to keratinocytes, and thicker epidermis and hyperkeratosis.

Front 8

Sunbeds

Back 8

UVA-induced tan only. So you don't get more melanocytes, more melanin synth, more transfer of melanosomes to keratinocytes, and thicker epidermis and hyperkeratosis.

So there is less protection when you get out into the real sun.

Front 9

Skin phototypes

Back 9

I - always burns never tans.
...
VI - never burns, always tans.

Front 10

Solar elastosis

Back 10

Elastosis in dermis causes thickening of skin.

Cutis rhomboidalis nuchae is when this is on the neck - makes it look leathery.

Front 11

Solar lengtigo and freckles

Back 11

Due to long term sun exposure

Front 12

Favre-Racouchot

Back 12

Chronic sun exp causes deep things usually on nails and cheeks.

Front 13

Poikiloderma of Civatte

Back 13

Reticulated reddish brown patches in neck.

Due to long term sun exposure.

Front 14

Risks of skin CA

Back 14

Basal cell CA is most common.

Also squamous cell CA and melanoma.

Front 15

Phototoxic rxn

Back 15

Chemical causes increased tendency to burn.

Can be due to topical agents or systemic agents (medications)

This can happen to anyone.

Front 16

Phytophotodermatitis

Back 16

Photoreactive agents in plants and fruits make you more susc to burn (e.g. limes)

Front 17

Photoallergy

Back 17

Antigen exposed to UVR turns into an antigen and then type IV hypersensitivity (T cell delayed type).

This is often topical and can spread beyond the area exposed to sun.

Front 18

Polymorphous light eruption

Back 18

Rxn to UVR in an otherwise healthy person. THought to be delayed hypersensitivity.

This is sun poisoning.

More often in females and fair skinned individuals.

Can present in many ways.

Front 19

Genetically inherited photodermatoses

Back 19

Erythropoetic porphyria

Xeroderma pigmentosum
Autosomal rec, mutation in DNA repair enzymes.

Front 20

Disorders aggravated by sun exposure

Back 20

Herpes flares, lupus, psoriasis (sometimes UV helps, but sometimes the psoriases goes to the area of injured skin)

Front 21

Phototherapy

Back 21

A narrow spectrum of UVB that reduces DNA synth and creates immune supp.

Give at sub-erythemogenic doses.

Tx of psoriasis, atopic dermatitis, mycosis fungoides, vitiligo, GVHD, pruritis, PMLE.

Front 22

UV exposure is a known risk factor for...

Back 22

melanoma.

Also inc risk of SCC and BCC

Many states regulate indoor tanning use by teens.

Front 23

Chemical sunscreen

Back 23

Absorbs light of specific wavelengths before it can interact with chromophores in the skin.

You want a broad spectrum that will get UVA and B

Front 24

UVB chemical sunscreens

Back 24

PABA esters, salicylates, cinnamates

Front 25

UVA chemical sunscreens

Back 25

Benzophenones, dibenzoylmethanes, mexoryl.

Front 26

Physical sunscreen

Back 26

particles scatter and reflect the full spectrum of UV light.

Examples are titanium dioxide and zinc oxide.

Front 27

Oxybenzone

Back 27

Stabilizes avobenzone so it is good to use these two together.

Front 28

SPF

Back 28

Ratio of the least amt of UVB to give erythema with sunscreen over without.

The UVA equiv is called protection factor of UVA (PFA)

SPF facts - as you get very high, it doesn't protect against all that much more UVB.

Front 29

Photoaging

Back 29

note that it incl solar elastosis, solar lentigo, ephelide, poikiloderma of civatte, favre-racouchot and colloid milium.

Front 30

Squamous cell ca more common in..

Back 30

pts with long term UVA and continuous sun exp

Front 31

Melanoma more common in...

Back 31

pts with blistering sunburns, intermittent intense UV exp, and fair skinned people near the equator.