Photodermatology

Question 1

What is Photobiology?

Answer 1

The study of non-ionising radiation on living organisms

Question 2

What is the most common cause of skin problems?

Answer 2

The sun

Question 3

What are the two classes of photosensitivity?

Answer 3

Normal and abnormal

Question 4

What classification is used for normal photosensitivity?

Answer 4

Fitzpatrick sun-reactive skin phototypes (SPT type I-IV, and sometimes V and VI)

Question 5

What are some treatment options for cutaneous photosensitivity?

Answer 5

Behavioural avoidance, clothing, sunscreen use, hardening, phototherapy, PUVA, chromophore removal, inhibition of mediator/action release, inhibition of inflammatory response

Question 6

What are the main types of Porphyrias?

Answer 6

Phototoxic skin porphyrias, Blistering and fragility skin porphyrias, acute attack porphyrias, severe congenital porphyrias

Question 7

What is an example of a phototoxic skin porphyria?

Answer 7

Erythropoietic protoporphyria

Question 8

Why is there sometimes no skin involvement in acute attack porphyrias?

Answer 8

Depends on where the block on the haem cascade is

Question 9

What are all porphyrias caused by?

Answer 9

Some kind of damage to enzymes in the Haem production pathway

Question 10

What is the most common porphyria?

Answer 10

Porphyria cutanea tarda

Question 11

What is needed to make a diagnosis of PCT type 1?

Answer 11

Both a diagnosis of the PCT itself and the diagnosis of the cause of the PCT

Question 12

What conditions normally lead to PCT type 1 being acquired?

Answer 12

Liver conditions (e.g alcoholic hepatitis)

Question 13

People heterozygous for what condition are likely to have PCT type 1?

Answer 13

Haemochromatosis

Question 14

What are some symptoms of PCT type 1?

Answer 14

Blisters, fragility, hyperpigmentation, hypertrichosis, solar urticaria, morphoea

Question 15

What kind of light causes PCT type 1?

Answer 15

Visible light (not UV)

Question 16

What mutation causes Erythropoietic protoporphoryia?

Answer 16

IVS3-48C allele trans to ferrochelatase mutation

Question 17

What other health problems do people with Erythropoietic protoporphoryia?

Answer 17

Anaemia, gallstones by age 40

Question 18

What are the symptoms of Erythropoietic protoporphoryia?

Answer 18

Pricking, burning sensation of skin on exposure to light, subtle pinkness to skin

Question 19

What investigation is done for PCT type 1?

Answer 19

Use Woods lamp to examine urine for porphyrins

Question 20

What is the management for PCT type 1?

Answer 20

Treat underlying cause and relieve skin disease

Question 21

What are some investigations done for Erythropoietic protoporphyria?

Answer 21

Quantitative RBC porphyrins, fluorocytes (patient/relatives), transaminases, [Hb], red cell indices (sometimes phototesting and biliary tract USS)

Question 22

Is Erythropoietic protoporphyria curable?

Answer 22

No-unless patient has bone marrow transplant

Question 23

What is the management for Erythropoietic protoporphyria?

Answer 23

Genetic counselling, 6 monthly LFTs and RBC porphyrins, visible light photoprotection measures

Question 24

What are some visible light photoprotection measures?

Answer 24

Avoid mid-day sun, wear dark clothes, use window films, apply topical sunscreen

Question 25

What conditions should acute intermittent porphyria being included in the list of differentials for?

Answer 25

Acute abdomen, mononeuritis multiplex, psychoses, Guillain-Barre syndrome

Question 26

What is unusual about acute intermittent porphyria?

Answer 26

It has no skin features