Porphyrias

Question 1

What are porphyrias?

Answer 1

A group of photosensitivity disorders resulting from an inherited or acquired defect in the enzymes required to produce adequate amounts of haem, with the subsequent accumulation of porphyrins

Question 2

Describe the porphyrin pathway of haem production

Answer 2

Question 3

What are some examples of porphyrias?

Answer 3

ALA-dehydrase deficiency porphyria
Acute intermittent porphyria
COngenital erythropoietic porphyria
Hereditary coproporphyria
Porphyria variegate
Erythropoietic protoporphyria

Question 4

What are the main groups of porphyrias?

Answer 4

• Phototoxic skin porphyria
• Blistering and fragility skin porphyrias
• Acute attack porphyrias (some with no skin involvement, some also cause blistering and fragility)
• Severe congenetial porphyria

Question 5

What is an example of a phytotoxic skin porphyria?

Answer 5

Erythropoietic protoporphyria

Question 6

What is an example of severe congenital porphyria?

Answer 6

Congenital erythropoietic porphyria

Question 7

What enzyme is deficient in acute intermittent porphyria?

Answer 7

Porphobilinogen deaminase

Question 8

What porphyrin accumulates in acute intermittent porphyria?

Answer 8

Porphobilinogen

Question 9

Who is most at risk of acute intermittent porphyria?

Answer 9

Females
30 years old

Question 10

How will acute intermittent porphyria present?

Answer 10

• Acute abdomen
• Mood disturbance
• Neurological
• Seizures
• Unlikely to cause skin symptoms

Question 11

What is the most common form of porphyria?

Answer 11

Porphyria cutanea tarda

Question 12

What enzyme is deficient in porphyria cutanea tarda?

Answer 12

Uroporphyrinogen decarboxylase

Question 13

What porphyrin is accumulated in porphyria cutanea tarda?

Answer 13

Uroporphyrinogen

Question 14

Who is most at risk of porphyria cutanea tarda?

Answer 14

Middle aged men
Those with liver disease

Question 15

How will porphyria cutanea tarda present?

Answer 15

• Blistering lesions on sun exposed sites that heal with scarring and are associated with hyper pigmentation
• Hypertrichosis
• Solar urticaria
• Morphoea

Question 16

What investigations are required in porphyria cutanea tarda?

Answer 16

• Bloods - porphyrin studies
• Woods lamp - urine shines pink instead of blue

Question 17

How is porphyria cutanea tarda managed?

Answer 17

Establish and treat the underlying cause - alcohol, viral hepatitis, oestrogens, haemachromatosis

Question 18

What causes erythropoietic protoporphyria?

Answer 18

Autosomal dominant mutation

Question 19

What enzyme is deficient in erythropoietic protoporphyria?

Answer 19

Ferrochelatase

Question 20

What porphyrin accumulates in erythropoietic protoporphyria?

Answer 20

Protoporphyrin IX

Question 21

How will erythropoietic protoporphyria present?

Answer 21

• There may be no evident rash but there will be burning and itching on the skin with sun exposure
• Typical presentation is child screaming when they are placed out in the sun

Question 22

What condition is shown?

Answer 22

Erythropoietic protoporphyria

Question 23

What investigations are required in erythropoietic protoporphyria?

Answer 23

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

Question 24

How is erythropoietic protoporphyria managed?

Answer 24

• 6 monthy LFTs and RBC porphrins
• Visible light photoprotection measures
• Prophylactic TL-01 phototherapy
• Antioxidants
• Avoid iron
• Incipient liver failure - oral charcoal, cholestyramine, ASA synthase inhibition
• Liver failure - liver transplant
• TiO2 and ZnO cream