Introduction to Photodermatology and Porphyrias

Question 1

What is photobiology defined as?

Answer 1

The study of non-ionising radiation on living systems

Question 2

What does photobiology encompass?

Answer 2

Botany, zoology, medicine

Question 3

What are photodermatoses?

Answer 3

Skin conditions with an abnormal reaction to light

Question 4

Shorter wavelengths of light have more ______

Answer 4

ENERGY

Question 5

Longer wavelengths of light have more __________

Answer 5

PENETRANCE

Question 6

Why may sparing of the area of skin behind the ear lead you to suspect photosensitivity?

Answer 6

The area of skin behind the ear is not usually exposed ti sunlight/light

Question 7

Why are there so many different porphyrias?

Answer 7

There is a huge range of enzymes in the pathway that converts glycine +succinyl CoA to Haem that can be missing or defective

Question 8

What is a porphyria?

Answer 8

A rare hereditary disease in which there is abnormal metabolism of the blood pigment haemoglobin.

Porphyrins are excreted in the urine, which becomes dark; other symptoms include mental disturbances and extreme sensitivity of the skin to light

A group of uncommon diseases caused by something going wrong with the production of chemicals known as porphyrins

Question 9

Porphyrias are due to abnormal metabolism of ___________

Answer 9

HAEMOGLOBIN

Question 10

Outline the 4 main groups of porphyrias.

Answer 10

1. Phototoxic
2. Blistering and fragility
3. Acute attack
4. Severe congenital

Question 11

Give an example of a phototoxic porphyria.

Answer 11

Erythropoietic protoporphyria

Question 12

Give an example of a congenital porphyria.

Answer 12

Congenital erythropoetic porphyria

Question 13

Describe what patients with a severe attack porphyria experience on exposure to light.

Answer 13

Prickly, burning pain on the exposed areas

Question 14

What are the 3 most common skin porphyrias in Scotland? Give the prevalence of each of these.

Answer 14

1. Porphyria cutanea tarda: 1 in 13,000 people
2. Erythropoietic protoporphyria: 1 in 43,000 people
3. Variegate porphyria: 1 in 244,000 people

Question 15

What does porphyria cutanea trade (PCT) type 1 occur due to’?

Answer 15

A liver disease that causes reduced activity of the enzyme uroporphyrinogen decarboxylase

This is an acquired form of the disease, not inherited

Question 16

What enzyme malfunctions in porphyria cutanea tarda type 1?

Answer 16

Uroprophyrinogen decarboxylase

Question 17

What does Uroprophyrinogen decarboxylase convert?

Answer 17

Uroporphyrinogen III TO Coprophyrinogen III

Question 18

What are the 2 steps in the diagnosis of PCT?

Answer 18

1 – diagnosis of PCT

2 – diagnosis of the cause(s) of PCT

Question 19

What skin layer does PCT disrupt?

Answer 19

DEJ

Question 20

Outline the typical presentation of PCT. Why?

Answer 20

BLISTERS AND FRAGILITY

Because it affects the DEJ

Question 21

Outline some other features that may be present in PC.

Answer 21

Hyperpigmentation
Hypertrichosis
Solar urticaria
Morphoea

Question 22

What is morphoea also known as? What is it

Answer 22

Localised scleroderma/ circumscribed scleroderma

Involves isolated patches of hardened skin

Question 23

How is suspected PCT investigated?

Answer 23

Using a Woods lamp – 410nm violent light shined onto samples, giving fluorescence

Question 24

Suggest possible underlying causes of PCT (remember that it is due to liver disease).

Answer 24

• Alcohol
• Viral hepatitis
• Oestrogens
• Haemochromatosis

Question 25

What are the 2 main aims of PCT treatment?

Answer 25

- Relieve the skin disease | - Treat the underlying skin diseases, to reduce the risk of liver cirrhosis, hepatoma etc

Question 26

What is erythropoietic protoporphyria caused by?

Answer 26

A deficiency of the enzyme Ferrochelatase which is responsible for the conversion of Protoporphyrin IX to Haem

Question 27

Describe the inheritance of erythropooietic protoporphyria.

Answer 27

Autosomal co-dominant

Question 28

Outline the presentation of erythropooietic protoporphyria.

Answer 28

Starts off like chicken pox/abnormal sensitivity to sun Sun causes tingling, itching or burning, red, swelling

Question 29

How long after sun exposure will erythropooietic protoporphyria develop?

Answer 29

After a few minutes and can often last for days

Question 30

People with EPP are often more sensitive to ___________

Answer 30

TEMPERATURE

Question 31

When does EPP usually start?

Answer 31

Childhood

Question 32

What investigations are used to aid in the investigation of suspected porphyrias?

Answer 32

``` Quantitative RBC porphyrins Fluorocytes (patient, relatives) Transaminases [Hb], red cell indices (Biliary tract USS) (Phototesting) ```

Question 33

How is erythropoietic porphyria managaed?

Answer 33

1. Explain diagnosis + council 2. 6 monthly LFT's and RBC's 3. Visible light porto-protection measures

Question 34

What can EPP be cured by? Is this worth the risk?

Answer 34

Bone marrow transplant - NO

Question 35

What can be given as prophylaxis in EPP?

Answer 35

TL-01 phototherapy

Question 36

What is the start of liver failure in EPP treated with?

Answer 36

Oral charcoal, cholestyramine, ALA synthase inhibition

Question 37

What is end stage liver failure in EPP treated with?

Answer 37

Liver transplant | Bone marrow transplant

Question 38

What is the 'sun-burning' part of the electromagnetic spectrum?

Answer 38

UVB light

Question 39

Give examples of photo-protection measures.

Answer 39

* Behavioural (e.g. avoid middle of day sunlight) * Clothing (importance of weave, colour, etc) * Environmental (e.g. shade trees, window films) * Topical sunscreen (not good at protecting from visible light as this needs to be reflected away)

Question 40

What are porphyrins?

Answer 40

The building blocks of haem, which, when combined with a protein (globin), forms haemoglobin

Question 41

What is the role of porphyrins in EPP?

Answer 41

In the case of EPP, there is a build-up of one of these porphyrins (protoporphyrin) in the blood, especially in the red blood cells This leads to a sensitivity to sunlight