Porphyrias Flashcards
Define Porphyrias
Group of diseases arising from enzyme deficiencies in haem synthesis pathway
What are possible symptoms of Porphyria?
Neurovisceral
eg Abdo pain, seizures, coma, psychiatric
Skin manifestations
Where is haem synthesised?
Mitochondria -> Cytosol -> Mitochondria
What is the most common porphyria?
Porphyria Cutanea Tarda
What precursor is responsible for neurovisceral symptoms?
ALA
What enzyme is deficient in Acute Intermittent Porpyria?
HMB Synthase
What 3 things can trigger Acute Intermittent Porphyria?
Drugs
Stress eg illness & surgery
Fasting
What investigation can confirm an episode of Acute Intermittent Porphyria?
Urine PBG
What symptom group is present in Acute Intermittent Porphyria?
Neurovisceral symptoms
What is the management of Acute Intermittent Porphyria?
IV Haem Arginate (Negative feedback)
IV carbohydrate
Avoid triggers
How do non-acute porphyrias present?
Photosensitive rash - blistering or non-blistering
What are the two acute porphyrias with cutaneous manifestations?
Hereditary Coproporphyria
Variegate Porphyria
Why do Hereditary Coproporphyria & Variegate Porphyria present with neurovisceral symptoms despite being far along the haem synthesis pathway?
The accumulated precursors exert negative feedback on HMB Synthase and lead to ALA accumulation
