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EMS - MoD > 15. Inborn Errors of Metabolism > Flashcards

15. Inborn Errors of Metabolism Flashcards

1
Q

Why are a lot of disorders that occur not seen?

A

As they are not compatible with life

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2
Q

What sometimes happens when compounds accumulate?

A

They can spontaneously convert into compounds that you don’t normally see - these may be toxic

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3
Q

Which substances often act as cofactors?

A

Vitamins or trace elements

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4
Q

Why can deficiency of vitamins and trace elements cause problems?

A

Vitamins and trace elements are often cofactors - lack of cofactors can lead to lack of activation of important enzymes

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5
Q

Give 3 mechanisms of disease

A
  • accumulation of a toxin
  • energy deficiency
  • deficient production of essential metabolite/structural component
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6
Q

Accumulation of a toxin can be a mechanism of disease. What accumulates in patients with urea cycle defects?

A

Ammonia (NH3) - very toxic

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7
Q

What are the clinical effects of acute hyperammonaemia toxicity?

A
  • lethargy
  • poor feeding
  • vomiting
  • tachypnoea
  • convulsions
  • coma
  • death
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8
Q

What is porphyria?

A

Disease in which there is abnormal metabolism of haemoglobin

Get accumulation of porphyrins

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9
Q

What are the 2 types of porphyria?

A
  • acute porphyria

- photosensitive porphyria

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10
Q

What are the steps in the pathway between ALA and HAEM?

A

ALA

PBG

Uroporphyrin

Coproporphyrin

Protoporphyrin

Haem

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11
Q

What are the signs of acute porphyria?

A
  • severe abdominal pain
  • pain in chest, legs, back
  • constipation or diarrhoea
  • vomiting
  • insomnia
  • palpitations
  • hypertension
  • anxiety or restlessness
  • seizures
  • mental changes
  • breathing problem
  • muscle pain/tingling/weakness/paralysis
  • red or brown urine
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12
Q

What are the signs of photosensitive porphyria?

A
  • sensitivity to light
  • sudden painful erythema and oedema
  • blisters taking weeks to heal
  • itching
  • fragile skin
  • increased hair growth
  • red or brown urine
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13
Q

Fatty acid oxidation results in what product?

A

Acetyl CoA

Goes on to make ketones or enter the TCA cycle

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14
Q

Fatty acid oxidation occurs in which organelle?

A

Mitochondria

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15
Q

What happens in androgen insensitivity syndrome?

A

Produces male hormones but lack the androgen receptor and so they therefore cannot use these male hormones and end up with a female phenotype

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16
Q

What are the characteristic of a genetic male with androgen insensitivity syndrome?

A
  • healthy female phenotype (normal breast development, absent pubic hair etc)
  • partial defect results in ambiguous genitalia
  • present with primary amenorrhea and infertility
  • usually need surgical resection of residual gonads
17
Q

What does the basic urine metabolism screen consist of?

A
  • spot tests
  • organic acids
  • amino acids
  • sugar chromatography
  • oligosaccharides/sialic acids
  • mucopolysaccharides
18
Q

How can amino acids be tested?

A

By amino acid TLC (thin layer chromatography)

  • can identity argininosuccinic acid which is a product of urea cycle defects
19
Q

What is homocystinuria?

A

A disorder of methionine metabolism, leading to an abnormal accumulation of homocysteine and its metabolites in urine

20
Q

What are the clinical problems of homocystinuria?

A
  • mental retardation
  • marfinoid habitus
  • ectopia lentis
  • osteoporosis
  • thromboembolism
21
Q

What is hyperhomocystinaemia?

A

Medical condition characterised by an abnormally high level of homocysteine in the blood, conventionally described as above 15 µmol/L

22
Q

What percentage of the general population have hyperhomocystinaemia?

A

5%

23
Q

There is increased incidence of hyperhomocystinaemia in patients with which diseases?

A
  • stroke
  • peripheral vascular disease
  • coronary artery disease
24
Q

What act as intermediates in most metabolic pathways?

A

Small molecular weight organic acids eg. amino acids, cholesterol, purines and pyrimidines, fatty acids, carbohydrates, neurotransmitters, drugs and diet, microorganisms

25
Q

The classic acidaemias are defects in what?

A

Branched chain amino acid catabolism

26
Q

What are the classic organic acidaemias?

A
  • propionic acidaemia
  • isovaleirc acidaemia
  • methyl malonic acidameia
27
Q

What are the benefits of diagnosis of IEMs?

A
  • treatment, improve prognosis
  • identify cause of clinical problem
  • genetic counselling
  • IEM act as models for other disorders
28
Q

How are neural tube defects diagnosed?

A
  • maternal serum and amniotic fluid AFP

- ultrasound scan at 16 weeks

29
Q

How is down syndrome diagnosed?

A

1st trimester - PAPA, HCG and nuchal translucency

2nd trimester - maternal serum AFP, HCG, inhibin and estriol

Test on the ascent: free foetal DNA

EMS - MoD (17 decks)

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