Chemical Pathology 7 - Porphyrias Flashcards

1
Q

What is haem?

A

Tetrapyrole rings surrounding a central iron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Roughly summarise the pathway of haem production

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

By what 2 factors are porphyrias classified?

A

Acute/ non-acute

Neurovisceral or cutaneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the cause of cutaneous symptoms in some porphyrias?

A

Porphyrin precursors build up under the skin and react with UV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which toxic product leads to neurovisceral symptoms in porphyria?

A

5-ALA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the most common porphyria?

A

Porphyria cutanea tarda

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the most common porphyria in children?

A

Erythropoietic protoporphyria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the symptoms of ALA synthase deficiency?

A

Weirdly, doesn’t cause porphyria!

Instead, causes an X-linked sideroblastic anaemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

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

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the symptoms of the acute neurovisceral porphyrias?

A

Motor neuropathy
Psychiatric symptoms
Severe abdominal pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

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

A

Drug that is CYP450 inducer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How can acute porphyria be diagnosed?

A

Urine left in light changes colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How should acute intermittent porphyria be managed?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

Hereditary coproporphyria

Variegate porphyria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

Blistering on back of hands (most exposed to UV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

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

17
Q

How can erythropoietic protoporphyria be diagnosed?

A

Undetectable in urine so will need to send blood

18
Q

What is the most common cause of porphyria cutanea tarda?

A

Liver disease