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Pathology (Guide) > Chemical Pathology - Porphyrias > Flashcards

Chemical Pathology - Porphyrias Flashcards

1
Q

What are porphyrias?

A

7 disorders caused by deficiency in enzymes, involved in haem biosynthesis, leading to build-up of toxic haem precursors

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2
Q

What are the three factors used to differentiate between the acute porphyrias?

A
  • Skin lesions: Present in HCP + VP only
  • Urine + faeces for porphyrins: Raised in HCP + VP only
  • Urine PBG: raised in all three
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3
Q

How is acute intermittent porphyria diagnosed?

A
  • Increased urinary porphobilinogen (PBG)
  • Increased aminolevulinic acid
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4
Q

What are some precipitating factors of acute intermittent porphyria?

A
  • ALA synthase inducers: steroids, ethanol, barbiturates
  • Stress: infection, surgery
  • Reduced calory intake + endocrine factors: premenstrual
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5
Q

What is the management of acute intermittent porphyria?

A
  • Avoid precipitating factors
  • Adequate nutrition + analgesia
  • Mx of underlying infection/illness
  • IV carbohydrate
  • IC haem arginate
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6
Q

What is the mode of inheritance of acute intermittent porphyria?

A

Autosomal dominant

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7
Q

What is the cause of acute intermittent porphyria?

A

HMB (hydroxymethylbilane) synthase deficiency

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8
Q

If a patient is hyponatraemic with acute intermittent porphyria, what condition is this indicative of?

A

SIADH

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9
Q

If a patient has a change in their urine colour + abdominal pain what condition is this indicative of?

A

Acute intermittent porphyria

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10
Q

Why are there no cutaneous manifestations of Acute intermittent porphyria?

A

There is an absence of porphyrinogens

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11
Q

What are some symptoms of acute intermittent porphyria?

A

Neurovisceral only (P’s):
- Painful abdomen
- Peripheral neuropathy
- Psychosis
- Port urine

  • Seizures
  • Muscle weakness
  • Constipation
  • Urinary incontinence
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12
Q

What is the mode of inheritance of hereditary coproporphyria (HCP)?

A

Autosomal dominant

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13
Q

What is the mode of inheritance of variegate porphyria (VP)?

A

Autosomal dominant

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14
Q

How does hereditary coproporphyria (HCP) manifest?

A

Neurovisceral:
- 4P’s (painful abdo, peripheral neuropathy, psychosis + port urine)

Skin Sx:
- Skin lesion fragility (skin lesions on back of hands, blister under the sun)

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15
Q

How does variegate porphyria (VP) manifest?

A

Neurovisceral:
- 4P’s (painful abdo, peripheral neuropathy, psychosis + port urine)

Skin Sx:
- Skin lesion fragility (skin lesions on back of hands, blister under the sun)

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16
Q

What is the investigation of choice for hereditary coproporphyria (HCP)?

A

Stool sample for coproporphyrinogen III

17
Q

What is the investigation of choice for variegate porphyria (VP)?

A

Stool sample for coproporphyrinogen III

18
Q

Which porphyrias manifest with skin lesions only (e.g. blistering skin lesion + pigmentation)?

A

Cutaneous Non-acute Porphyrias
- Porphyria Cutanea Tarda (PCT)
- Erythropoeitic Protoporphyria (EPP)
- Congenital erythropoeitic porphyria (CEP)

19
Q

What are the commonest + second commonest porphyrias?

A

Commonest: Porphyria Cutanea Tarda
2nd Commonest: Acute Intermittent Porphyria

20
Q

What is the cause of porphyria cutanea tarda?

A

Uroporphyrinogen decarboxylase deficiency

21
Q

How does porphyria cutanea tarda present?

A
  • Photosensitivity
  • Facial hyperpigmentation
  • Hypertrichosis
  • Blistering
  • Milia
  • Scarring
  • Exacerbated by alcohol
22
Q

What investigations/results are seen in porphyria cutanea tarda?

A
  • Increased urinary uroporphyrins
  • Increased urinary coproporphyrins (pink red fluorescence with Wood’s lamp)
  • Increased ferritin
  • Abnormal LFTs
23
Q

What is the management of porphyria cutanea tarda?

A
  • Avoid sun + precipitants (alcohol, hepatitis C, HIV)
  • Chloroquine
24
Q

What is the clinical manifestation of erythropoeitic protoporphyria and which population is it most commonly seen in?

A
  • Found in children
  • Cutaenous erythema without blisters/bullae
25
Q

Why can’t you test urine in erythropoeitic protoporphyria?

A

protoporphyrin is lipophilic

26
Q

What investigations are used to diagnose erythropoeitic protoporphyria?

A

RBC protoporphyrin levels

27
Q

What is the clinical manifestation of congenital erythropoeitic porphyria?

A

cutaenous erythema with blistering

Pathology (Guide) (84 decks)

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