Porphyrias

Question 1

What is meant by cutaneous photosensitivity?

Answer 1

Abnormal skin reaction to UV, and sometimes visible, light

Question 2

What is porphyria?

Answer 2

Hereditary disease where there is build up of porphyrins, caused by reduced enzyme activity in the haem pathway
These react with light to produce skin reactions

Question 3

Name the 3 most common porphyrias

Answer 3

Porphoryia cutanea tarda
Erythropoietic protoporphyria
Variegate porphyria

Question 4

How does porphyria cutanea tarda arise?

Answer 4

Reduced activity of uroporphyrinogen decarboxylase causes build up of uroporphyrins that react with light
(URO –> CoPRO)

Question 5

List symptoms of porphyria cutanea tarda

Answer 5

Blistering
Skin fragility
Hyperpigmentation
Hypertrichosis

Question 6

List 4 causes of porphyria cutanea tarda

Answer 6

Alcohol
Viral hepatitis
High oestrogen
Haemachromatosis

Question 7

How does erythropoietic protoporphyria arise?

Answer 7

Reduced activity of ferrochelatase causes build up of protoporphyrins
(PROTOP –> HAEM)

Question 8

List symptoms of erythropoietic protoporphyria

Answer 8

Swelling/burning
Itching
Pain

Question 9

How does acute intermittent porphyria arise?

Answer 9

Reduced activity of PBG deaminase causes build up of uroporphyrins
(PBG –> HMB)