Porphyrias Flashcards
what are porphyrias
disorders cauased by deficinecy in enzymes needed for haem synthesis, causing toxic precursors to build up.
Affect synthesis of haem molecule needed for haemoglobin, p450 enzymes & peroxidases
what are porphyrias split into? what is the main difference?
acute & non-acute porphyrias.
non-acute only give skin lesions
inheritance pattern of acute porphyrias
autosomal dominant
most common acute porphyria?
acute intermittent prophyria
how does acute intermittent porphyria present?
abdominal pain + psychiatric disturbances + seizures
(no skin lesions)
what triggers acute intermittent porphyria
certain meds, fasting, alcohol
what enzyme is dysfunctional in acute intermittent porphyria and what builds up
-porphobilinogen deaminase (PBG deaminase)
-ALA builds up (neurotoxic)
how does hereditary coproporphyria present?
similar to acute intermittent (abdo pain, psychiatric, seizure) + skin lesions
how does variegate porphyria present?
similar to AIP but with skin lesions + photosensitivity
what enzyme is dysfunctional in hereditary coproporphyria?
coproporphinogen oxidase
what enzyme is dysfunctional in variegate prophyria?
protpoporphyrogen oxidase
how to differentiate between acute porphyrias?
AIP = no skin lesions
HCP + VP = skin lesions
urine PBG raised in all 3
check urine & faeces for porphyrins (high in HCP + VP, not high in AIP)
(porphyrins later on in chain)
what will be raised in acute porphyrias
urinary PBG
what are the non-acute (chronic) porphyrias?
-congenital erythropoetic porphyria (CEP)
-erythropoietic protoporphyria (EPP)
-porphyria cutanea tarda (PCT)
what is the most common porphyria overall
porphyria cutanea tarda
