Photosensitivity and the Porphyrias

Question 1

What are the porphyrias?

Answer 1

A group of diseases which are caused due to an inborn error in the haem metabolism pathway, leading to the build-up of intermediate metabolites

Question 2

How does porphyria cutanea tarda present?

Answer 2

Blistering, erosions and often milia on the face and backs of hands

Question 3

How do sporadic cases of porphyria cutanea tarda classically show up in male and females respectively?

Answer 3

Males - Chronically high alcohol intake

Females - Taking oestrogen medications

Question 4

Which porphyria is most common in Scotland?

Answer 4

Porphyria cutanea tarda

Question 5

How is acute intermittent porphyria inherited?

Answer 5

AD

Question 6

In which area of the world is acute intermittent porphyria particularly common?

Answer 6

Scandinavia

Question 7

How does acute intermittent porphyria present?

Answer 7

Abdominal pain attacks

Neuropsychiatric symptoms

Dark urine

NO skin lesions

Question 8

What actually causes the damage when porphyrins build up in the skin?

Answer 8

Sunlight activates porphyrins which promotes mediator release from surrounding inflammatory cells leading to a damaging inflammatory response

Question 9

In which country is Variegate prophyria most common?

Answer 9

South Africa

Question 10

How does varigate porphyria present?

Answer 10

Symptoms of both porphyria cutanea tarda and acute intermittent porphyria

1. Blistering, erosis and milia on the face and backs of hands
2. Acute abdominal pain, dark urine, neuropsychiatric symptoms

Question 11

What are porphyrins?

Answer 11

Intermediates within the haem synthesis pathway

Molecules are roughly circular in shape and may react to EM radiation

Question 12

How is congenital erythropoietic porphyria inherited?

Answer 12

AR

Question 13

Which enzyme in the haem synthesis pathway has undergone a mutation in congenital erythropoietic porphyria?

Answer 13

Uroporphyrinogen III co-synthase

Question 14

Congenital erythropoietic porphyria involves a build up of which porphyrin in the body?

Answer 14

Hydromethylbilane

Question 15

How does congenital erythropoietic porphyria present?

Answer 15

Blistering (and scarring) of the skin

Hairy skin

Brown teeth

Haemolytic anaemia

Pink fluorescing urine

Question 16

How many enzymes are in the haem synthesis pathway?

Answer 16

8

Question 17

The lak of activity from which enzyme is responsible for causing porphyria cutanea tarda?

Answer 17

Uroporphyrinogen decarboxylase

Question 18

Which colour will a patient’s urine fluoresce under Wood’s lamp if they are suffering from porphyria cutanea tarda?

Answer 18

Coral pink

Question 19

Which inherited porphyria is most common in Scotland?

Answer 19

Erythropoietic protoporphyria

(porphyria cutanea tarda is the most common overall by 80% of cases are sporadic)

Question 20

Why may nerve damage occur in a patient with acute intermittent porphyria?

Answer 20

There is a build up of porphobilnogen (PBG) due to lack or absence of functioning PBG deaminase

Question 21

Eryhtropoietic and erythrohepatic protoporphyrias are most highly sensitive to which type of EM radiation?

Answer 21

UV B

Question 22

At which stage in life does erythropoeitic protoporphyria present?

Answer 22

Early childhood

Question 23

How does erythropoeitic protoporphyria present?

Answer 23

Discomfort, itch or tingling in sun exposed skin

There are often no clinical signs

Question 24

Build up of which porphyrin, and lack of which functioning enzyme, causes erythropoietic protoporphyria?

Answer 24

Lack of ferrochelatase activity

Build up of protoporphyrin IX