Porphyrias Flashcards
(32 cards)
How are the majority of Porphyrias inherited?
Autosomal dominant fashion
What is a key indicator of a porphyria?
Having differently coloured skin, urine, teeth which are a result of the toxic byproducts of build up of heme synthesis precursors
Why can we not have a Porphyria of the ALAS enzyme in the pathway?
This would be incompatible with life
What enzymes in the synthesis pathway are considered to be early lesion enzymes?
ala dehydratase and porphobilinogen deaminase
what does a lesion in ala dehydratase lead to accumulation of?
ALA
what does a lesion in porphobilinogen deaminase lead t o an accumulation of?
Porphobilinogen
what are the build up products of the early lesion enzymes toxic too?
they are neurotoxic specifically to the nerves in the abdomen
what are the symptoms of a early lesion porphyria attack?
severe abdominal pain, hallucinations, vomiting, constipation, diarrhoea.
What is there a decreased level of in early lesion prophyrias
Reduced heme in body cells and body fluids
What is an example of a porphyria that is considered to be an early lesion porphyria?
Acute intermittent Porphyria.
Why is the oral contraceptive risk for those who have AIP?
in a study this triggered an attack in 24% of women who took the pill
What two things are measured to diagnose AIP?
you would do a PBGD assay from PBGD taken from erythrocyte cells to diagnose type 1 and 3 AIP
you can also measure urinary levels of PBG and ALA.
What is the prevalence of AIP
1 in 10,000 people in the UK have this gene defect but only 1 in many thousands actually go on to have an attack
What do later legions in the heme synthesis pathway produce?
build up of metabolically useless Porphyrins
what enzyme is affected in congenital erythropoietic porphyria?
uroporphyrinogen 3 co synthase
what classes of porphyringoen are produced in later lesion porphyrias?
class one instread of class 3
what are the class 3 porphyrinogens made into?
they are autooxidised to make metabolically useless and toxic porphyrins
what are the main symptoms of congential erythropoietic porphyria?
red pee
fluorescent teeth
Photosensitivity
anaemia
how many recognised porphyrias are there?
8
What is the most common kind of porphyria?
Porphyria cutanea tarda
what enzyme is affected in pct and whaht does this cause the build up of?
uroporphyrinogen decarboxylase which leads to build up of uroporphyrinogen 3 which then gets oxidised to useless type 1 Porphyrins.
how would you diagnose this?
red wine coloured pee with excess uroporphyrin 1 in urine
also you can look for elevated uroporphyrins in the faeces and in the plasma.
what is the first type of porphyria cutanea tarda characterised by?
its not genetics,but there is decreased activity of hepatic uroporphyrinogen decarboxylase
what is the the second type of porphyria cutanea tarda caused by?
by an autosomal dominant mutation that results in overall decreased acitvity of uroporphyrinogen activity in all cells.
