Skin Porphyrias Flashcards
What are porphyrias
Group of photosensitivity disorder that result from the inherited or acquired defect of an enzyme that is required to produce adequate amounts of haem.
The enzyme defect results in the accumulation of porphyrins that are chromophores (chemicals that absorb radiation)
What are the 4 main groups of porphyria’s? Provide an example for each
Phototoxic skin porphyria
e.g erythropoietic protoporphyria
Blistering and fragility skin porphyrias
e.g. porphyria cutanea tarda
Acute attack porphyria (may or may not involve skin)
e.g. acute intermittent porphyria
Severe congenetial porphyria
e.g. congeniterythropoietic porphyria
Erythropoietic vs hepatic porphyria
Erythropoietic - problem mainly in bone marrow
hepatic - problem mainly in liver
what enzyme deficiency causes porphyria cutanea tarda
uroporphyrinogen decarboxylase (UPDC)
What porphyrin accumulates in porphyria cutanea tarda
uroporphyrinogen
Who does porphyria cutanea tarda typically affect
Middle aged men
Is porphyria cutanea tarda typically erythropoietic or hepatic in nature
Hepatic
What disease is porphyria cutanea tarda typically associated with
Liver disease e.g. haemochromatosis, hepatitis, alcoholism
Porphyria cutanea tarda clinical features
- Blistering lesions on sun exposed sites
- Blisters scarring with hyper pigmentation
- Hypertrichosis
- Morphoea (localised scleroderma)
- Solar urticaria
Porphyria cutanea tarda investigations
- Bloods: porphyrin studies
- Woods lamp: urine shines pink instead of blue
In porphyria cutanea tarda what colour does urine shine with a woods lamp
Pink
Porphyria cutanea tarda treatment
Treat underlying cause - alcohol, viral hepatitis, oestrogens, haemachromatosis
Who does erythropeotic protoprophyria tend to affect
Children
What type of inheritance is erythropeotic protoprophyria
Autosomal dominant
What enzyme is deficient in erythropeotic protoprophyria
Ferrochelatase
What porphyrin is accumulated in erythropeotic protoprophyria
Protoporphyrin IX
Erythropeotic protoprophyria clinical features
- Burning & itching of skin on sun exposure
- May or may not have a rash
- Child may scream when out in the sun
Erythropeotic protoprophyria investigations
- quantitative RBC porphyrins
- test for fluorescent erythrocytes (flurocytes)
- phototesting
- test for complications
- Biliary tract USS (for gallstones)
- transaminases (for liver disease)
Erythropeotic protoprophyria treatment
- 6 monthly LFTs and RBC porphrins
- Visible light photoprotection measures
- Prophylactic TL-01 phototherapy
- Antioxidants
- Avoid iron
Why should patients with EPP avoid iron
Enzyme defect:
- EPP is caused by a genetic defect in the enzyme ferrochelatase (FECH), which is responsible for inserting iron into protoporphyrin IX to form heme.
PPIX buildup:
- When FECH activity is reduced, protoporphyrin IX accumulates in red blood cells, making them sensitive to light.
Iron supplementation risk:
- Providing additional iron to someone with EPP can further increase the pool of available protoporphyrin IX, potentially worsening their photosensitivity symptoms.
Why can antioxidants help patients with EPP
EPP is characterized by a build-up of a photosensitizing molecule called protoporphyrin IX, which when exposed to light, generates harmful reactive oxygen species (ROS);
Antioxidants can neutralize these ROS, mitigating the severe skin reactions that EPP patients experience upon sun exposure.
What can be used in patients with EPP & early or late stage liver failure
- Early - oral charcoal, cholestyramine, ASA synthase i.
- Late - liver transplant
