Porphyrias Flashcards
Defective enzymes in what metabolic pathway give rise to porphyrias?
Haem formation
Describe the main categories of Porphyrias
- Phototoxic skin porphyrias
- Blistering and fragility skin porphyrias
- Acute attack porphyrias
- Severe congenital porphyrias
What enzyme is absent in Acute Intermittent Porphyria?
PBG Deaminase
=> build up of Porphobilinogen (PBG)
What enzyme is absent in Congenital Erythropoietic Porphyria?
Uroporphyrinogen III synthase
=> Build up of hydroxymethylbilane
If the enzyme Uroporphyrin Decarboxylase is not present, what can this cause?
Build up of Uroporphyrinogen III
=> Porphyria Cutanea Tarda
=> Hepato-erythropoietic Porphyria
A defect in what enzyme causes erythropoeitic protoporphyria?
Ferrochelatase
=> Build up of Protoporphyrin IX
A defect in what enzyme causes Variegate porphyria?
Protoporphyrin oxidase
=> build up of Protoporphyrinogen IX
How common is Porphyria Cutanea Tarda in Scotland?
1 in 13,000
How common is Erythropoietic protoporphyria in Scotland?
1 in 43,000
How common is Variegate porphyria in Scotland?
1 in 244,000
How does Porphyria Cutanea Tarda usually present?
- blisters/ fragility
- Hyperpigmentation
- Hypertrichosis
- Solar urticaria
- Morphoea
What investigation can be used to diagnose Porphyria Cutanea Tarda?
Woods Lamp
(UV light shone through urine sample, if sample becomes red, this shows a build up of uroporphyrinogen III which is excreted in the urine)
another test can also be undertaken to find the exact wavelengths of light reflected from the sample
Give some examples of causes of Porphyria Cutanea Tarda?
Alcohol
Viral hepatitis
Oestrogens
Haemochromatosis
What investigations can be used when erythropoeitic protoporphyria is suspected?
Quantitative RBC porphyrins Fluorocytes Transaminases [Hb] red cell indices Biliary tract US Phototesting
How is erythropoeitic protoporphyria managed?
6 monthly LFTs and RBC porphyrins
Visible light photoprotection measures
