Porphyrias Flashcards
What are porphyrias?
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
Describe the porphyrin pathway of haem production
What are some examples of porphyrias?
ALA-dehydrase deficiency porphyria
Acute intermittent porphyria
COngenital erythropoietic porphyria
Hereditary coproporphyria
Porphyria variegate
Erythropoietic protoporphyria
What are the main groups of porphyrias?
- 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
What is an example of a phytotoxic skin porphyria?
Erythropoietic protoporphyria
What is an example of severe congenital porphyria?
Congenital erythropoietic porphyria
What enzyme is deficient in acute intermittent porphyria?
Porphobilinogen deaminase
What porphyrin accumulates in acute intermittent porphyria?
Porphobilinogen
Who is most at risk of acute intermittent porphyria?
Females
30 years old
How will acute intermittent porphyria present?
- Acute abdomen
- Mood disturbance
- Neurological
- Seizures
- Unlikely to cause skin symptoms
What is the most common form of porphyria?
Porphyria cutanea tarda
What enzyme is deficient in porphyria cutanea tarda?
Uroporphyrinogen decarboxylase
What porphyrin is accumulated in porphyria cutanea tarda?
Uroporphyrinogen
Who is most at risk of porphyria cutanea tarda?
Middle aged men
Those with liver disease
How will porphyria cutanea tarda present?
- Blistering lesions on sun exposed sites that heal with scarring and are associated with hyper pigmentation
- Hypertrichosis
- Solar urticaria
- Morphoea
What investigations are required in porphyria cutanea tarda?
- Bloods - porphyrin studies
- Woods lamp - urine shines pink instead of blue
How is porphyria cutanea tarda managed?
Establish and treat the underlying cause - alcohol, viral hepatitis, oestrogens, haemachromatosis
What causes erythropoietic protoporphyria?
Autosomal dominant mutation
What enzyme is deficient in erythropoietic protoporphyria?
Ferrochelatase
What porphyrin accumulates in erythropoietic protoporphyria?
Protoporphyrin IX
How will erythropoietic protoporphyria present?
- 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
What condition is shown?
Erythropoietic protoporphyria
What investigations are required in erythropoietic protoporphyria?
- Quantitative RBC porphyrins
- Flurocytes (patient, relatives)
- Transaminases
- [Hb], red cell indices
- Biliary tract USS
- Phototesting
How is erythropoietic protoporphyria managed?
- 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
