Porphyrias Flashcards
Acute Intermittent Porphyria is characterized by which enzyme defect and what compounds are increased?
PBG deaminase and the compounds that are increased are PBG and ALA. It is autosomal dominant.
What treatment should be implemented urgently for acute hepatic prophyria attacks? What enzyme is inhibited w/this treatment?
Hemin therapy. Delta-aminolevulinic acid synthetase.
What is the enzyme defect in porphyria cutanea tarda and what is the mode of inheritance?
Uroporphyrinogen decarboxylase, it is autosomal dominant.
What are some precipitating factors of porphyria cutanea tarda?
Iron overload-most important cause (HFE), alcohol, estrogen, Hepatitis C, HIV.
How do you establish the diagnosis of porphyria cutanea tarda?
elevated levels of urinary uroporphyrin more than coproporphyrin.
What is the treatment for porphyria cutanea tarda?
Avoid precipitating factors such as sunlight. Use opaque sunblock. Use phlebotomy until in remission. Or iron chelators if can’t do phlebotomy.
How do you make the diagnosis of AIP?
The urine will be positive for high PBG and ALA. In the blood (RBC) the PBG demainase activity will be low.
When screening for porphyria during an acute attack if the PBG is elevated what is the best next step in management?
Implement Hemin therapy. Make sure to collect serum/fecal prophyrin levels before starting treatment though.
Clinically what do you see with AIP and what clinical feature do these patients not have (similar to what you see with ADP)?
These patients strictly have neurovisceral attacks with NO skin symptoms. ADP patients present similarly.
With the exception of ADP with the other acute hepatic porphyrias what are the characteristic lab features?
They will all have increased urine PBG and ALA levels. ADP will only have elevated ALA levels, PBG will be NORMAL.
What are the clinical features of VP and HCP?
They both have neurovisceral attacks in combination with skin lesions. Remember that VP is common in South Africans.
With acute hepatic porphyrias what are some options to help with preventing an attack?
Regular transfusions of Hemin, OCPs (to help stop ovulation), and Givosiran (siRNA directed against ALAS1 mRNA).
What can you remember to help you differentiate between the enzyme def in VCP vs HCP?
It’s in the name. Hereditary Coproporphyria-coproporphyrinogen oxidase def. VP-protoporphyrinogen oxidase
With cutaneous porphyrias what are their main symptoms?
With cutaneous porphyrias they only have skin manifestations, they do not have neurovisceral attacks.
