photosensitive skin disease

Question 1

what UV type can penetrate deeper into the skin and why can it do this

Answer 1

UVA - due to its longer wavelength

Question 2

negative effects of sun exposure (5)

Answer 2

1. sunburn
2. epidermal hyperplasia
3. skin ageing (photoageing)
4. DNA damage -> mutation -> carcinogenesis
5. immune suppression -> abnormal cell proliferation -> carcingogenesis

Question 3

which UV is responsible for vit B synthesis

Answer 3

UVB

Question 4

top 4 Vit D containing foods

Answer 4

dairy, fish (oily), fortified cereals, legumess

Question 5

what is sunburn

Answer 5

erythema and vasodilation of the skin caused by excessive exposure to UV radiation

Question 6

sunburn presentation

Answer 6

tender, hot to touch, blistering, erythematous -> followed by desquamation and pigmentation

Question 7

what is polymorphic light eruption

Answer 7

“prickly heat” - and itchy erythematous ereuptions (plaques, papules etc. - ‘polymorphic’) that spares exposed areas (hands/face)

Question 8

polymorphic light eruption pathophys

Answer 8

thought to be a type IV hypersensitivity reaction to UV radiation (usually UVA); failure of immune suppression results in this rash

Question 9

how to distinguish whether a reaction is to UVA or UVB

Answer 9

only UVA will penetrate windows; monochromator testing

Question 10

treatment for polymorphic light eruption

Answer 10

1. avoidance/sunblock;
2. topical/oral steroids (severe);
3. prophylactic UVB/UVA - desensitisaton

Question 11

what is chronic actinic dermatitis

Answer 11

a skin disorder in which the skin, particularly on sunlight exposed areas, becomes inflamed and develops eczema

Question 12

chronic actinic dermatitis presentation

Answer 12

itchy, erythamotous, thickened xeroderma on sun exposed skin

Question 13

investigations for chronic actinic dermatitis

Answer 13

photo-patch testing (same as patch testing but UVA light is included in sample of triggers)

Question 14

chronic actinic dermatitis treatment

Answer 14

1. sunavoidance/sunblock
2. same as eczema - emollient, topical steroids, immunesuppression (v. severe)
3. may need to put special film over windows

Question 15

what is solar urticaria

Answer 15

a rare physical urticaria where weals develop within minutes of UV exposure

Question 16

solar urticaria treatment

Answer 16

1. sun protection/avoidance
2. antihistamine
3. desensitising phototherapy

Question 17

what is actinic prurigo

Answer 17

a type of photosensitivity causing itchy papules on sun exposed areas (commonly lips and face) - usually manifests in childhood

Question 18

what kind of people does actinic prurigo usually affect

Answer 18

children with darker skin types

Question 19

actinic prurigo treatment

Answer 19

1. emollients;
2. topical steroids
3. hydroxychloroquine
4. desensitisation

Question 20

what is hydroa vacciniforme

Answer 20

a condition where blisters form over sun exposed areas; heals with scaring; seen in girls ages 3-15yro usually

Question 21

hydroa vacciniforme presentation

Answer 21

burning/itching sensation 30-120mins after exposure -> leads to blister formation

Question 22

hydroa vacciniforme treatment

Answer 22

1. sun protection/avoidacne
2. desnsensitising phototherapy
3. hydroxychloroquine(rare)

Question 23

whats is xeroderma pigmentosum

Answer 23

a rare autosomal recessive defect in DNA repair resulting in photosensitivity, skin ageing and a tendancy to skin cancers (cancer seen in v young pts)

Question 24

xeroderma pigmentosum Mgx

Answer 24

1. sun avoidacne
2. regular skin examinations

Question 25

what is the most common subtype of cutneous prophyria and how does it present

Answer 25

porphyria cutanea tarda (PCT) - presents with erythema, blisters, erosions and hypertrichosis in response to UV raditaion/minor trauma, often seen on hands, face, neck etc.

Question 26

what can cause PCT

Answer 26

1. inherited (autosomal dominant);
2. sporadic (associated w alcohol, oestrogen, iron overload, pesticides)

Question 27

investigations of porphyria

Answer 27

1. biopsy
2. urine sample (look for prophyrins and check w woods light - fluoresces coral pink)
3. Hb and ferratin levels
4. viral hepatitis screen
5. fasting blood glucose
6. check for ANA

Question 28

treatments for cutaneous porphyria

Answer 28

manage underlying conditions/triggers
1. avoid alcohol
2. oestrogens
3. adjust iron levels
4. sun block/avoidance
5. hydroxychloroquine

Question 29

a defect in what enzyme is associated with porphyria cutanea tarda

Answer 29

uroporphyrin decarboxylase (in the uroporphyrin III -> coproporphyrinogen III step)

Question 30

4 other kinds of porphyria

Answer 30

1. erythropoieti protoporphyria (autosomal dominant, presents in infancy);
2. acute intermittent porphyria (autosomal dominant, skin lesions not usually seen but abdominal pain is)
3. variegate porphyria (combination of PCT and AIP symptoms)
4. pseudoprophyria (normal metabolism but presents w prophyria symptoms)

Question 31

what dugs can cause drug induced lupus

Answer 31

hydralazine, barbamaxepine, lithium, phenytoin, sulphonamides, minocycline

Question 32

phototoxic vs photoallergic reaction

Answer 32

phototoxic - exaggerated sunburn reaction, minutes to hours after exposure;
photoallerguc - only happens in people sensitised to the allergen , may spread to no exposed areas, +ve photopatch test seen

Question 33

examples of drugs that cause photosensitivity (8)

Answer 33

1. Abx - doxycyline
2. NSAIDs
3. retinoids (isotretanoid, acitretin)
4. hypoglycaemics
5. anticonvulsants
6. components of some sunscreens (PABA, benzophenones)
7. oral contraceptive pill
8. coal tar

Question 34

what is phytophotodermatitis

Answer 34

a condition where organic psoralens (found it lime, celery, wild carrot etc.) come into contact w pts and cause a blistering eruption when they then go into UV light