Chemical Pathology 7 - Porphyrias Flashcards Preview

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Flashcards in Chemical Pathology 7 - Porphyrias Deck (18)
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1

What is haem?

Tetrapyrole rings surrounding a central iron

2

Roughly summarise the pathway of haem production

ALA + ALA --> PBG
PBG --> HMB
HMB --> EITHER uroporphyriogen 1 or 3
Uroporphyrinogen 3 --> haem

3

By what 2 factors are porphyrias classified?

Acute/ non-acute
Neurovisceral or cutaneous

4

What is the cause of cutaneous symptoms in some porphyrias?

Porphyrin precursors build up under the skin and react with UV

5

Which toxic product leads to neurovisceral symptoms in porphyria?

5-ALA

6

What is the most common porphyria?

Porphyria cutanea tarda

7

What is the most common porphyria in children?

Erythropoietic protoporphyria

8

What are the symptoms of ALA synthase deficiency?

Weirdly, doesn't cause porphyria!
Instead, causes an X-linked sideroblastic anaemia

9

What are the 2 types of acute neurovisceral porphyria, which enzyme deficiency causes each, and how can they be clinically differentiated?

Acute intermittent porphyria (most common) = HMB synthase deficiency - causes ATTACKS
ALA dehydratase porphyria = PBG synthase deficiency - more one acute episode than numerous attacks

10

What are the symptoms of the acute neurovisceral porphyrias?

Motor neuropathy
Psychiatric symptoms
Severe abdominal pain

11

What is the most likely cause of an acute intermittent porphyria 'attack'?

Drug that is CYP450 inducer

12

How can acute porphyria be diagnosed?

Urine left in light changes colour

13

How should acute intermittent porphyria be managed?

Avoid attacks (adequate nutrition, precipitant drugs, prompt treatment)
IV carbs OR
IV haem arginate

14

Recall 2 forms of porphyria that have acute neurovisceral AND cutaneous symptoms

Hereditary coproporphyria
Variegate porphyria

15

How do the cutaneous effects of porphyrias usually present and why?

Blistering on back of hands (most exposed to UV)

16

Recall the 3 forms of non-acute porphyria, and which of these conditions causes blistering

Congenital eryhtropoietic porphyria (blistering)
Porphyria cutanea tarda (blistering)
Erythropoietic protoporphyria (blistering)

17

How can erythropoietic protoporphyria be diagnosed?

Undetectable in urine so will need to send blood

18

What is the most common cause of porphyria cutanea tarda?

Liver disease

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