Intro to Phototoxicity and the Porphyrias

Question 1

what are the 2 different types of cutaneous photosensitivity

Answer 1

phototoxicity and photoallergy

Question 2

what is the scale used to identify normal cutaneous photosensitivity

Answer 2

Fitzpatrick sun-reactive skin phototypes

I to IV, sometimes V and VI used

Question 3

a 32 year old exposed to 1 hour midday sun gets sunburn and then tans afterwards, what type of skin phototype is he

Answer 3

II

Question 4

which skin site is a clue to cutaneous photosensitivity

Answer 4

retroauricular(behind the ear)

Question 5

what is involved in all the skin porphyrias

Answer 5

all involve porphyrines as chromophores, the chemicals that absorb radiation

Question 6

where do manifestations of porphyrias arise

Answer 6

where the porphyrines accumulate, whcih depends on how water or fat soluble they are

Question 7

what are the 4 main groups of porphyrias

Answer 7

phototoxic skin porphyrias
blistering + fragility skin porphyrias
acute attack porphyrias
severe congenital porphyrias

Question 8

what are the more common features of skin porphyrias

Answer 8

skin blistering and fragility, and acute phototoxicity

Question 9

how common are skin porphyrias in Scotland

Answer 9

rare

most common is porphyria cutanea tarda which is 1 in 13,000 people

Question 10

which enzyme has reduced activity in porphyria cutanea tarda(PCT)

Answer 10

uroporphyrinogen synthase

Question 11

what type of porphyria is porphyria cutanea tarda(PCT)

Answer 11

hepatic(problem mainly in liver)

Question 12

what are the clinical features of porphyria cutanea tarda (PCT

Answer 12

typical; blistering(unilocular), fragility

also; hyperpigmentation, hypertrichosis, solar urticaria, morphoea

Question 13

what investigation is used for PCT

Answer 13

woods lamp

Question 14

what are the aims of treatment of PCT

Answer 14

relive the skin disease, treat underlying disease

Question 15

what are some underlying causes of PCT

Answer 15

alcohol, viral hepatitis, oestrogens, haemochromatosis

Question 16

what enzyme has reduced sensitivity in erythropoietic protoporphyria and what does it cause

Answer 16

ferrochelatase has reduced sensitivity, causes build up of protoporphyrin

Question 17

what inheritance pattern is seen in erythropoietic protoporphyria

Answer 17

autosomal dominant

Question 18

what is involved in the clinical presentation of erythropoietic protoporphyria

Answer 18

irritation + burning pain on skin(non-blistering) on exposure to sunlight

Question 19

what investigations are used for diagnosis of erythropoietic protoporphyria

Answer 19

fluorescence of peripheral RBCs and detection of increased protoporphyrin in RBCs and stool

Question 20

what is involved in the management of erythropoietic protoporphyria

Answer 20

6 monthly LFTs and RBC porphyrins, and visible light photoprotection measures
also prophylactic UVB phototherapy and anti-oxidants can be used

Question 21

what are some photoprotection measures

Answer 21

behavioural(eg avoid sunlight), clothing, environmental(eg window films), topical sunscreen