Photosensitivity and the Porphyrias Flashcards

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1
Q

What are the porphyrias?

A

A group of diseases which are caused due to an inborn error in the haem metabolism pathway, leading to the build-up of intermediate metabolites

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2
Q

How does porphyria cutanea tarda present?

A

Blistering, erosions and often milia on the face and backs of hands

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3
Q

How do sporadic cases of porphyria cutanea tarda classically show up in male and females respectively?

A

Males - Chronically high alcohol intake

Females - Taking oestrogen medications

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4
Q

Which porphyria is most common in Scotland?

A

Porphyria cutanea tarda

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5
Q

How is acute intermittent porphyria inherited?

A

AD

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6
Q

In which area of the world is acute intermittent porphyria particularly common?

A

Scandinavia

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7
Q

How does acute intermittent porphyria present?

A

Abdominal pain attacks

Neuropsychiatric symptoms

Dark urine

NO skin lesions

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8
Q

What actually causes the damage when porphyrins build up in the skin?

A

Sunlight activates porphyrins which promotes mediator release from surrounding inflammatory cells leading to a damaging inflammatory response

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9
Q

In which country is Variegate prophyria most common?

A

South Africa

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10
Q

How does varigate porphyria present?

A

Symptoms of both porphyria cutanea tarda and acute intermittent porphyria

  1. Blistering, erosis and milia on the face and backs of hands
  2. Acute abdominal pain, dark urine, neuropsychiatric symptoms
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11
Q

What are porphyrins?

A

Intermediates within the haem synthesis pathway

Molecules are roughly circular in shape and may react to EM radiation

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12
Q

How is congenital erythropoietic porphyria inherited?

A

AR

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13
Q

Which enzyme in the haem synthesis pathway has undergone a mutation in congenital erythropoietic porphyria?

A

Uroporphyrinogen III co-synthase

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14
Q

Congenital erythropoietic porphyria involves a build up of which porphyrin in the body?

A

Hydromethylbilane

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15
Q

How does congenital erythropoietic porphyria present?

A

Blistering (and scarring) of the skin

Hairy skin

Brown teeth

Haemolytic anaemia

Pink fluorescing urine

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16
Q

How many enzymes are in the haem synthesis pathway?

A

8

17
Q

The lak of activity from which enzyme is responsible for causing porphyria cutanea tarda?

A

Uroporphyrinogen decarboxylase

18
Q

Which colour will a patient’s urine fluoresce under Wood’s lamp if they are suffering from porphyria cutanea tarda?

A

Coral pink

19
Q

Which inherited porphyria is most common in Scotland?

A

Erythropoietic protoporphyria

(porphyria cutanea tarda is the most common overall by 80% of cases are sporadic)

20
Q

Why may nerve damage occur in a patient with acute intermittent porphyria?

A

There is a build up of porphobilnogen (PBG) due to lack or absence of functioning PBG deaminase

21
Q

Eryhtropoietic and erythrohepatic protoporphyrias are most highly sensitive to which type of EM radiation?

A

UV B

22
Q

At which stage in life does erythropoeitic protoporphyria present?

A

Early childhood

23
Q

How does erythropoeitic protoporphyria present?

A

Discomfort, itch or tingling in sun exposed skin

There are often no clinical signs

24
Q

Build up of which porphyrin, and lack of which functioning enzyme, causes erythropoietic protoporphyria?

A

Lack of ferrochelatase activity

Build up of protoporphyrin IX