Porphyrias and photodermatology Flashcards
What is photobiology?
The study of non ionizing radiation on living systems
What is photdermatoses?
Skin conditions where UV radiation is the causitive agent
What are the different types of fitzpatrick sun-reactive skin phototypes?
Type 1 - will burn and never tan
Type 2 - will burn and sometimes tan
Type 3 - will usually tan
Type 4 - will never burn
What are some treatment options for photosensitivity?
Behavioural avoidance Clothing Sunscreen use Phototherapy Chromophore removal Inhibition of mediator Inhibition of inflammatory response
What are porphyrias?
Disorders resulting from low levels of enzymes responsible for the 5th step in heme production
What are the different types of porphyrias?
Erythropoietic protoporphyria
Blistering and fragility skin porphyrias
Acute attack porphyrias
Severe congenital prophyrias
What is porphyria cutanea tarda?
Combination of liver inflammation and liver iron overload that reduces the action of enzymes causing porphryia
What is the biochemical pathway for porphyria?
PCT is caused by partial inactivation of an enzyme called uroporphyrinogen decarboxylase (UROD) leading to a build up of porphyrins in the liver from which they overflow into the blood stream and thus reach the skin.
They concentrate in the DEJ causing blistering
What liver conditions can exacerbate PCT?
Excess alcohol consumption
Haemachromatosis
Viral infections of the liver such as hep C
Oestrogen therapy; combined pill or HRT
What are the symptoms of PCT?
Blisters Fragility Hyperpigmentation Hypertrichosis Solar uricaria Morphoea Dark urine
How is PCT diagnosed?
Levels of polyphyria in blood
Woods lamp - urine is flourscent
What are the aims of treatment in PCT?
Relieve the skin condition
Treat underlying disease to reduce risk of liver cirrhosis, hepatoma etc
What is is erythropoietic protoporphyria?
Build up of protoporphyrin in the red blood cells leading to a sensitivity to sunlight. This is due to a lack of ferrochelatase which usualyl converts protoporphyin into haem by adding iron
How does EPP lead to photosensitivity?
As blood passes through the skin, protoporphyrin absorbs the energy from sunlight and sets a chemical reaction damaging the skin
The nerve endings perieve this as itching or burning pain
What type of light is EPP sensitive to?
UVA and visible light
What are the symptoms of EPP?
Photosensitivity
How is EPP diagnosed?
Levels of porphyrins in blood Transaminases Hb for anaemia Biliary tract USS Phototesting
What systemic condition can EPP cause?
Gallstones
Liver failure
How is EPP managed?
6 monthly LFTs and RBC porphyrins Visible light photoprotection Prophylactic TL-01 phototherapy Anti-oxidants Avoid iron
What should be considered in a differential of AIP?
Acute abdomen
Monoeuritis multiplex
Guillain-barre
Psychoses
Enzyme deficient in acute intermittent porpyria
Deficiency in PBG de-aminase
Presentation of acute intermittent porpyria
Severe abdo pain Constipation N+V Hyponatraemia Tachycardic Hypotensive NO SKIN PROBLEMS
What type of UV radiation causes problems in porphyria?
UVA
Enzyme deficiency in PCT
Uroporphyrinogen decarboxylase
Presentation of PCT?
Blisters
Fragility
Hypertrichosis
Solar urticaria
How is PCT diagnosed?
Coral pee
What enzyme is deficient in erythropoietic protophyria?
Ferrochelatase
Presentation of erythropoietic protoporphyria?
Tingling Itching burning Redness Swelling after sun Anaemia CHILDHOOD
How are porphyrias treated?
Sun avoidance and visible light sun cream
