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MBD/MI (Wothaya) > Inborn Errors Of Metabolism > Flashcards

Inborn Errors Of Metabolism Flashcards

1
Q

How do inborn errors of metabolism (IEM) affect the organism?

A

Toxic accumulation of substrates
Defects in energy production/ use due to deficiency of products
Or a combination of the two

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2
Q

What things can accumulate toxically in inborn errors of metabolism?

A

Substrates

Intermediates from alternative metabolic pathways

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3
Q

What can inborn errors of metabolism vary in?

A

Age of onset and clinical severity

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4
Q

What are the four disorders studied in the croonian lectures?

A

Alkaptonuria
Cystinuria
Albinism
Pentosuria

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5
Q

What did Archibold Garrod propose the disorders were?

A

Congenital
Inborn
Followed mendels laws of inheritance

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6
Q

Who came up with the one gene - one enzyme concept?

A

Beadle and tatum

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7
Q

What does the one gene-one enzyme concept mean?

A

One mutated gene causes a non functional enzyme

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8
Q

What is an example of molecular disease concept?

A

Gene mutations produce an alteration in the primary structure of proteins by hamoglobin in sickle cell diesase

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9
Q

What are the four mechanisms of inheritance?

A

Autosomal recessive
Autosomal dominant
X-linked
Mitochondrial

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10
Q

Who transfers autosomal recessive inheritance?

A

Both parents carry a mutation affecting the same gene

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11
Q

What is the risk size in each autosomal recessive pregnancy?

A

1 in 4

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12
Q

What increases the risk of autosomal recessive conditions?

A

Cosanguinity

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13
Q

What are some examples of autosomal recessive diseases?

A

PKu, alkaptonuria, McADD

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14
Q

Are autosomal dominant conditions rare or common in IEMs?

A

Rare

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15
Q

What are some examples of autosomal dominant diseases?

A

Marfans, acute intermittent porphyria

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16
Q

How are X-linked mutations passed down?

A

Maternal line

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17
Q

Where do X-linked diseases appear and where are they carried?

A

Appear in men, carried in women

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18
Q

What are some examples of X-linked conditions?

A

Fabrys disease, ornithine carbamoyl transferase deficiency

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19
Q

Where are mitochondrial diseases inherited from?

A

Mother

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20
Q

Which gender do mitochondrial diseases affect?

A

Male and female offspring

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21
Q

Why are mitochondrial diseases exclusively inherited from the mother?

A

Only the egg contributes mitochondria to the developing embryo

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22
Q

What are some examples of mitochondrial IEM diseases?

A

MERFF and MELAS

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23
Q

What does MERFF stand for?

A

Myoclonic epilepsy and red ragged fibre disease

24
Q

What does MERFF cause?

A

Deafness, dementia, seizures

25
Q

What does MELAS stand for?

A

Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes

26
Q

How do you establish the pattern of inheritance?

A

Accurate family history

27
Q

What determines the presentation of mitochondrial inheritance?

A

Distribution of affected mitochondria

28
Q

What are more frequently affected in mitochondrial inheritance?

A

High-energy requiring organs

29
Q

What are IEM treated by?

A

Dietary control restriction and/or compound supplementation

30
Q

What are the classifications of IEM?

A

Toxic accumulation
Deficiency in energy production/utilisation
Disorders of complex molecules involving organelles

31
Q

What are the types of toxic accumulation?

A

Protein metabolism

Carbohydate intolerance

32
Q

What are the categories of deficiency in energy production/utilisation IEMs?

A

Fatty acid oxidation
Carbohydrate utilisation/production
Mitochondrial disorders

33
Q

What is an example of a fatty acid oxidation deficiency IEM?

A

MCADD

34
Q

What is an example of a deficiency of carbohydrate utilisation/production?

A

GSD

35
Q

What are the deficiencies of mitochondria?

A

MERFF

36
Q

What is an example of a lysosomal storage disorder?

A

Fabrys

37
Q

What is an example of a peroxisomal disorder?

A

Zellwegers

38
Q

How do IEM present?

A

Depends on the severity of the metabolic defect

39
Q

What are neonatal IEMs often caused by?

A

Defects in carb intolerance and energy metabolism

40
Q

What are late onset IEMs caused by?

A

Accumulation of toxic molecules

41
Q

What do late onset IEMS present with?

A

Organ failure, encephalopathy and seizures

42
Q

When do IEM symptoms start to present in neonates?

A

First week of life when starting full milk feeds

43
Q

What are the clues for IEM?

A

Cosanguinity
Family history of similar illness and siblings or unexplained deaths
Infants who was well at birth and starts to deteriorate for no obvious reason

44
Q

What are the clinical scenarios of neonate IEM presentation?

A 
Poor feeding, lethargy, vomiting
Epileptic encephalopathy
Profound hypotonia
Organomegaly
Dysmorphic features
Sudden unexpected death in infancy
45
Q

What are the biochemical abnormalities in neonate IEM presentation?

A

Hypoglycaemia
Hyperammonia
Unexplained metabolic acidosis/ketoacidosis
Lactic acidosis

46
Q

What are the routine blood tests for IEMs?

A

Blood gas
Blood glucose and lactate
Plasma ammonia

47
Q

What are the specialist lab investigations for IEMs?

A 
Plasma amino acids
Urinary organic and orotic acid
Blood acyl carnitines
Urinary glycosaminoglycans
Plasma very long chain fatty acids
CSF tests
48
Q

What are the confirmatory investigations that you can do for IEM?

A

Enzymology
Biopsy
Fibroblasts studies
Mutation analysis (WGS)

49
Q

What are the wilson and junger criteria for screening?

A

Condition should be an important health problem
Must know prevelence in screening population
History of condition understood
Easy and reliable screening test
Availibility of an accepted treatment
Diagnosis and treatment should be cost effective

50
Q

What conditions are tested for in newborn blood spot screening?

A 
PKU 
congenital hypothyroidism 
Sickle cell disease
Cystic fibrosis
MCADD
51
Q

When are newborn blood spot screening samples taken?

A

Day 5 (day of birth is day 0)

52
Q

What are the guidlines for a good quality bloodspot of newborn blood spot screening?

A

All four circles on ‘guthrie’ card need to be completely filled with a single drip of blood which soaks through to the back of the card

53
Q

What is Tyrosinaemia type 1?

A

Genetic deficiency in fumarylacetoacetase

54
Q

What is the function of fumarylacetoacetase?

A

Catalyses the final step in tyrosine metabolism

55
Q

What is the treatment for tyrosinaemia type 1 and how does it work?

A

Nitisinone inhibits an earlier step in the pathway to prevent accumulation of toxic metabolites

56
Q

What are the symptoms of ornithine transcarbamylase deficiency?

A

Ataxia,
seizures,
Hyperammonaemic encephalopathy

57
Q

What can trigger a hyperammonaemic crisis?

A

Increased endogenous protein catabolism (infection, fasting, trauma, steroid administration)
High protein intake

MBD/MI (Wothaya) (57 decks)

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