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Dermatology > Photodermatoses > Flashcards

Photodermatoses Flashcards

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Dermatology Board Prep flashcards
1
Q

What is photo dermatology

A

The interaction between non-ionising radiation and the skin - includes UV

Also includes the use of light radiation for diagnostic and therapeutic cases

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2
Q

What is the Fitzpatrick scale

A

A scale of skin types by how photosensitive they are
Dependent on the level of melanin
Class 1 is most likely to burn etc
Class 6 is black skin

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3
Q

What is the cause of many porphyrias

A

A defect in one of the enzymes in the haem pathway
Leads to a build up of porphyrins
Different enzyme defects cause different types

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4
Q

What are the 4 main groups of porphyrias

A

Photo toxic skin porphyria - erythropoietic
Blistering and skin fragility porphyria
Acute attack
Severe congenital

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5
Q

How do you diagnose porphyria cutanea tarda

A

Look for clinical signs - blisters, fragile skin (often on backs of hands) in response to sun exposure
Plasma scan - will show abnormal porphyrins
Take a urine sample and shine a woods lamp through it - the excess porphyrins cause it to go a different colour

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6
Q

What are some non-skin affects of erythropoietic protoporphyria

A

Mild anaemia
Gallstones
Rarely liver failure

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7
Q

What investigations can be done for EPP

A

Quantative RBC porphyrins
Transaminases
Flurocytes

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8
Q

What can be done to manage EPP

A

Genetic counselling and advice on condition
6 months of LFT and RBC porphyrin checks
Protection from visible light - long, dark clothing etc
Phototherapy - exposure to build tolerance
Anti-oxidants

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9
Q

List some protective measures from UV light

A

Behavioural - avoiding midday
Clothing
Environmental - staying in shade, having blinds drawn
Sunscreen

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10
Q

What are the benefits of UV exposure

A 
Vitamin D synthesis - sun is our main source 
Heat
Vision
Circadian rhythms
Bactericidal
Therapeutic & diagnostic use
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11
Q

What are the risks of UV exposure

A 
Sunburn
Eyes - conjunctivitis, keratitis, cataract (only visible light reaches retina)
Skin cancer - BCC, SCC, melanoma
Photoageing
Photosensitivity - photodermatoses
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12
Q

What types of UV reach us on earth

A

UVA - can get through windows
UVB - only on sunniest days and blocked by glass etc.

UVC is filtered by ozone

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13
Q

Which type of UV is more biologically active - A or B

A

UVB is more biologically energetic – need less to burn you

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14
Q

What type of UV is used in sunbeds and what are the risks

A

UVA

Melanoma & non-melanoma skin cancer - complete carcinogen if used regularly before the age of 35

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15
Q

What types of UV are used in therapy

A

Phototherapy - mainly narrowband UVB

Photochemotherapy - Psoralen + UVA
PUVA

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16
Q

Describe the use of PUVA in skin condiitons

A

PUVA is used if not responding to other treatments– second line

Give UVA alongside psoralen, a plant based chemical which is good at sensitising to UVA
Allows a small dose of UVA therapy to be effective

Risk of SCC - not used if need many rounds and fair skinned

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17
Q

Describe the onset and peak of UVB sunburn

A

Onset 2-4 h

Peak 12-24 h

18
Q

How does UV exposure cause immunosuppression

A

APC and langerhan’s migrate to the local lymph nodes in response to exposure so the skin loses it immune cells – Won’t mount a proper reaction as fewer cells

May get false negative patch test reactions - delay if patient has been on holiday

19
Q

UV exposure causes immunosuppression - true or false

A

True

20
Q

What is the main genetic photodermatosis and how does it present

A

Xeroderma pigmentosum
Rare, autosomal recessive
Failure of DNA excision repair - cannot repair sun damage
Rapid photoageing of skin and skin cancer - mel and non-melanoma
Death in teens

21
Q

What is a polymorphic light eruption

A

Type IV cell mediated hypersensitivity reaction to sunlight
Develop an itchy rash in sun exposed areas a few hours after exposure
Delayed onset papules & vesicles
Non-scarring

22
Q

Who gets affected by polymorphic light eruptions

A

Females

In first 3 decades of life

23
Q

It is possible for those with polymorphic light eruptions to become desensitised - true or false

A

True

May not have it forever

24
Q

How do you differentiate PLE and prickly heat

A

Prickly heat only in folds

PLE in sun exposed areas

25
Q

How can you diagnose PLE

A

UVA provocation test

Basically a patch test with UVA exposure - look for reaction

26
Q

What is actinic prurigo

A

An immune photodermatosis
Seen in kids - mainly in south america
HLA type association
Intensely itchy rash in response to sun exposure

27
Q

What is chronic actinic dermatitis

A

An immune photodermatosis
Light sensitivity eczema
Need significant exposure to trigger

28
Q

What is solar urticaria

A

An immune photodermatosis
Type I IgE mediated reaction to sunlight (UVA)
UVA so can be affected through windows
Occurs after minutes but also disappears quicky

29
Q

What is phytophotodermatitis

A

Light reaction due to plant chemical exposure

Seen with lime and celery

30
Q

Which drugs can induce photosensitivity

A 
Antibiotics - sulphonamides, tetracyclines, fluoroquinolones
Diuretics
NSAIDs
Quinine
Amiodarone
31
Q

Porphyria cutanea tarda is associated with which other conditions

A

Iron overload & liver disease
Alcohol
Hepatitis C,
Haemochromatosis

32
Q

How does EPP present in the skin

A

Pain on sun exposure – presents in children, scream when in the sun

33
Q

Which other skin conditions can be aggravated by the sun

A 
Eczema and psoriasis
Lupus erythematosus
Rosacea
Pemphigoid, pemphigus
Erythema multiforme
34
Q

How do you investigate photosensitivity

A 
Monochromator phototesting
Provocation test
Minimal erythema dose (MED) test
Patch & photopatch tests
Porphyrins, lupus studies
HLA status
Histology
35
Q

How do sunscreens work

A

Sunscreen chemicals absorb (eg. oxybenzone)

Or reflect light (eg. titanium dioxide)

36
Q

What are the main roles of vitamin D

A

Increase the flow of calcium into the bloodstream, by promoting absorption of calcium and phosphorus from food in the intestines, and reabsorption of calcium in the kidneys
Enables normal mineralization of bone.

37
Q

what is the active hormonal form of vitamin D

A

Cacitriol

Produced in the liver and kidney from Vit D3

38
Q

What does vit D deficiency cause

A

Rickets in children

Osteomalacia in adults

39
Q

Who is at risk of sun-induced skin cancer

A

Fair skin
Personal or family history of skin cancer
Lots of moles - >50
Those on immunosuppressive treatment

40
Q

List signs of photoageing

A

solar elastosis: skin coarse and yellow, loses elastic quality
Irregular pigmentation, freckling, lentigo
Telangiectasia and atrophy, easy bruising
Roughness, dryness
Deep wrinkling

41
Q

which conditions can be treated by phototherapy

A

Inflammatory skin disease. e.g. moderate to severe psoriasis and dermatitis

Dermatology (14 decks)

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