Photodermatology Flashcards
What is Photobiology?
The study of non-ionising radiation on living organisms
What is the most common cause of skin problems?
The sun
What are the two classes of photosensitivity?
Normal and abnormal
What classification is used for normal photosensitivity?
Fitzpatrick sun-reactive skin phototypes (SPT type I-IV, and sometimes V and VI)
What are some treatment options for cutaneous photosensitivity?
Behavioural avoidance, clothing, sunscreen use, hardening, phototherapy, PUVA, chromophore removal, inhibition of mediator/action release, inhibition of inflammatory response
What are the main types of Porphyrias?
Phototoxic skin porphyrias, Blistering and fragility skin porphyrias, acute attack porphyrias, severe congenital porphyrias
What is an example of a phototoxic skin porphyria?
Erythropoietic protoporphyria
Why is there sometimes no skin involvement in acute attack porphyrias?
Depends on where the block on the haem cascade is
What are all porphyrias caused by?
Some kind of damage to enzymes in the Haem production pathway
What is the most common porphyria?
Porphyria cutanea tarda
What is needed to make a diagnosis of PCT type 1?
Both a diagnosis of the PCT itself and the diagnosis of the cause of the PCT
What conditions normally lead to PCT type 1 being acquired?
Liver conditions (e.g alcoholic hepatitis)
People heterozygous for what condition are likely to have PCT type 1?
Haemochromatosis
What are some symptoms of PCT type 1?
Blisters, fragility, hyperpigmentation, hypertrichosis, solar urticaria, morphoea
What kind of light causes PCT type 1?
Visible light (not UV)
What mutation causes Erythropoietic protoporphoryia?
IVS3-48C allele trans to ferrochelatase mutation
What other health problems do people with Erythropoietic protoporphoryia?
Anaemia, gallstones by age 40
What are the symptoms of Erythropoietic protoporphoryia?
Pricking, burning sensation of skin on exposure to light, subtle pinkness to skin
What investigation is done for PCT type 1?
Use Woods lamp to examine urine for porphyrins
What is the management for PCT type 1?
Treat underlying cause and relieve skin disease
What are some investigations done for Erythropoietic protoporphyria?
Quantitative RBC porphyrins, fluorocytes (patient/relatives), transaminases, [Hb], red cell indices (sometimes phototesting and biliary tract USS)
Is Erythropoietic protoporphyria curable?
No-unless patient has bone marrow transplant
What is the management for Erythropoietic protoporphyria?
Genetic counselling, 6 monthly LFTs and RBC porphyrins, visible light photoprotection measures
What are some visible light photoprotection measures?
Avoid mid-day sun, wear dark clothes, use window films, apply topical sunscreen
What conditions should acute intermittent porphyria being included in the list of differentials for?
Acute abdomen, mononeuritis multiplex, psychoses, Guillain-Barre syndrome
What is unusual about acute intermittent porphyria?
It has no skin features
