Photodermporphyrias Flashcards
what is photobiology?
the study of non-ionization on living systems
what are photodermatoses?
damage/diseases caused by exposure to light
rashes etc
does wavelength affect the type of photodermatoses?
yes
diff parts of spectrum cause different photodermatoses
give an example of normal cutaneous photosensitivity
sun burn
how is cutaneous photosensitivity classified?
Fitzpatrick classification
skin phototypes 1-4 (burn - tan)
describe mechanism of photodermatoses development
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)
what is porphyria?
group of disorders causing skin or nerve problems
caused by problem with enzymes in metabolism of glycine + succinyl CoA to Haem
what are the 4 groups of porphyrias?
phototoxic skin porphyrias
blistering and fragility skin porphyrias
acute attack porphyrias
severe congenital porphyrias
give 2 common features of skin porphyria?
blistering and fragility
pain, pricking and burning
what is porphyria cutanea tarda (PCT)?
most common skin porphyria
caused by low levels of enzyme responsible for fifth step in haem production
what are the 2 steps in PCT diagnosis?
diagnosis of PCT
diagnosis of the cause of PCT
how does PCT present?
blisters morphoea (hard epidermal obtrusions) hyperpigmentation hypertrichosis (excessive hair) solar urticaria in areas of skin exposed to sunlight (back of hands, face etc)
how is PCT investigated?
woods lamp
PCT glows red/pink colour
how does woods lamp diagnose different conditions?
different skin conditions glow a different colour under the blacklight
each wavelength corresponds to a disease
what can cause PCT?
alcohol
viral hepatitis
oestrogens
haemochromatosis
what is the treatment for PCT?
no cure
relieve the symptoms of the skin disease
treat underlying cause (reduce risk of cirrhosis etc)
what is erythropoietic protoporphyria?
porphyria caused by lack of enzyme responsible for 6th and final step of haem synthesis
less common than PCT
what causes erythropoietic protoporphyria?
autosomal co-dominant inheritance of low enzyme levels
what are the symptoms of erythropoietic protoporphyria?
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
how is erythropoietic protoporphyria diagnosed?
woods lamp (glows blue)
RBC porphyrin levels
transaminases
flourocytes (not used often)
how is erythropoietic protoporphyria managed?
6 monthly LFTs and RBC porphyrins reduce exposure to visible light (clothing, stay in shade, Dundee cream) TL-01 phototherapy anti-oxidants avoid iron
what is Dundee cream?
type of topical sunscreen with larger particles that protects against visible light (unlike commercial sunscreen)
what could acute intermittent porphyria be mistaken for?
acute abdomen
guillain barre
psychoses
