Photodermporphyrias

Question 1

what is photobiology?

Answer 1

the study of non-ionization on living systems

Question 2

what are photodermatoses?

Answer 2

damage/diseases caused by exposure to light

rashes etc

Question 3

does wavelength affect the type of photodermatoses?

Answer 3

yes

diff parts of spectrum cause different photodermatoses

Question 4

give an example of normal cutaneous photosensitivity

Answer 4

sun burn

Question 5

how is cutaneous photosensitivity classified?

Answer 5

Fitzpatrick classification

skin phototypes 1-4 (burn - tan)

Question 6

describe mechanism of photodermatoses development

Answer 6

light penetrates skin
chemical in skin absorbs light which changes the chemical causing it to release inflammatory mediators
the following inflammatory response causes damage
(can be treated at each step)

Question 7

what is porphyria?

Answer 7

group of disorders causing skin or nerve problems

caused by problem with enzymes in metabolism of glycine + succinyl CoA to Haem

Question 8

what are the 4 groups of porphyrias?

Answer 8

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

Question 9

give 2 common features of skin porphyria?

Answer 9

blistering and fragility

pain, pricking and burning

Question 10

what is porphyria cutanea tarda (PCT)?

Answer 10

most common skin porphyria

caused by low levels of enzyme responsible for fifth step in haem production

Question 11

what are the 2 steps in PCT diagnosis?

Answer 11

diagnosis of PCT

diagnosis of the cause of PCT

Question 12

how does PCT present?

Answer 12

blisters
morphoea (hard epidermal obtrusions)
hyperpigmentation
hypertrichosis (excessive hair)
solar urticaria
in areas of skin exposed to sunlight (back of hands, face etc)

Question 13

how is PCT investigated?

Answer 13

woods lamp

PCT glows red/pink colour

Question 14

how does woods lamp diagnose different conditions?

Answer 14

different skin conditions glow a different colour under the blacklight
each wavelength corresponds to a disease

Question 15

what can cause PCT?

Answer 15

alcohol
viral hepatitis
oestrogens
haemochromatosis

Question 16

what is the treatment for PCT?

Answer 16

no cure
relieve the symptoms of the skin disease
treat underlying cause (reduce risk of cirrhosis etc)

Question 17

what is erythropoietic protoporphyria?

Answer 17

porphyria caused by lack of enzyme responsible for 6th and final step of haem synthesis
less common than PCT

Question 18

what causes erythropoietic protoporphyria?

Answer 18

autosomal co-dominant inheritance of low enzyme levels

Question 19

what are the symptoms of erythropoietic protoporphyria?

Answer 19

often not much to see so can me late to diagnose
generally just hypersensitivity to the sun (i.e very fast burning, swelling etc)
sometimes hyperpigmentation

Question 20

how is erythropoietic protoporphyria diagnosed?

Answer 20

woods lamp (glows blue)
RBC porphyrin levels
transaminases
flourocytes (not used often)

Question 21

how is erythropoietic protoporphyria managed?

Answer 21

6 monthly LFTs and RBC porphyrins
reduce exposure to visible light (clothing, stay in shade, Dundee cream)
TL-01 phototherapy
anti-oxidants
avoid iron

Question 22

what is Dundee cream?

Answer 22

type of topical sunscreen with larger particles that protects against visible light (unlike commercial sunscreen)

Question 23

what could acute intermittent porphyria be mistaken for?

Answer 23

acute abdomen
guillain barre
psychoses