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FS Chemical Pathology > Metabolic Disorders and Screening 1 and 2 > Flashcards

Metabolic Disorders and Screening 1 and 2 Flashcards

1
Q

What are the criteria for screening programmes called?

A

Wilson and Junger

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2
Q

What causes Phenylketonuria (PKU)?

A

Deficiency of phenylalanine hydroxylase

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3
Q

What does phenylalanine do?

A

Converts phenylalanine to tyrosine

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4
Q

What are key clinical features of PKU?

A 
Low IQ
Seizures
Stunted growth
Hyperactivity
Musty odor of breath/skin/urine
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5
Q

How is PKU treated?

A

Monitor diet closely
Monitor phenylalanine intake
Treatment must be started within first 6 weeks of life

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6
Q

What is sensitivity?

A

True positives/total number of disease cases

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7
Q

What is specificity?

A

True negatives/total number without the disease

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8
Q

What is the positive predictive value?

A

True positives/total number with positive results

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9
Q

What is the Guthrie test and when is it done?

A

UK Newborn Screening
Heel prick test
Blood sample to screen for abnormalities
5-8 days of life

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10
Q

What illnesses are in the Newborn screening programme?

A 
Congenital hypothyroidism
Sickle cell disease
Cystic fibrosis
A series of metabolic disorders:
MCAD deficiency
Maple syrup urine disease
Isovaleric acidaemia
Glutaric aciduria type 1
Homocystinuria
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11
Q

What is MCAD deficiency?

A

Fatty acid oxidation disorder

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12
Q

What does MCADD classically result in?

A

Cot death due to hypoglycaemia

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13
Q

What gene is affected in cystic fibrosis?

A

Cystic fibroiss transmembrane conductance regulator (CFTR)

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14
Q

What test is used to screen for CF?

A

High immune reactive trypsinogen

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15
Q

What mutation most commonly causes CF?

A

Delta F508

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16
Q

What is the urea cycle responsible for?

A

Breaking down ammonia into urea

17
Q

How many enzymes are in the urea cycle?

A

7

18
Q

What is the genetic inheritance of urea cycle disorders?

A

Autosomal recessive except ornithin transcarbamylase (OTC) deficiency which is X-linked

19
Q

How does the body react to hyperammonimia?

A

Attach glutamine to ammonia to make glutamine

20
Q

What can be measured in the urine to look for urea cycle disorders?

A

Orotic acid

21
Q

How are urea cycle disorders treated?

A

Remove the ammonia: sodium benzoate, sodium phenylacetate, or dialysis
Reduce ammonia production: low protein diet

22
Q

With what groups of condition can hyperammonaemia be associated?

A

Long-term psychiatric illness

23
Q

What are key features of urea cycle disorders?

A 
Vomiting without diarrhoea
Respiratory alkalosis
Hyperammonaemia
Neurological encephalopathy
Avoidance of protein
24
Q

What is an organic aciduria?

A

A defect within the complex metabolism of branched chain amino acids (leucine, isoleucine, and valine)

25
Q

What are the amino acids excreted as in organic aciduria?

A

3-OH-isovaleric acid (cheesy/sweaty smell)

Isovaleryl glycine

26
Q

How does a neonate present with organic aciduria?

A 
Unusual odour 
Lethargy
Feeding problems
Truncal hypotonia
Myoclonic jerks
Hyperammonaemia with metabolic acidosis and high anion gap
27
Q

What is Reye’s syndrome?

A 
A rare disorder causing swelling of the brain and liver. 
Features include: 
- Vomiting
- Lethargy
- Confusion
- Decerebration
- Respiratory arrest

Can be triggered by drugs (salicylates) and viral illness.

28
Q

What is included in a Reye Syndrome metabolic screen?

A 
During acute episode:
Plasma ammonia
Plasma/urine amino acid
Urine organic acids
Plasma glucose and lactate

Any time:
Blood spot carnitine profile

29
Q

What do mitochondrial fatty acid beta-oxidation defects cause?

A

Hypoketotic hypoglycaemia - unable to break down fatty acids

30
Q

What do mitochondrial fatty acid beta-oxidation disorders do to the body?

A

Hepatomegaly

Cardiomyopathy

31
Q

How many disorders of galactose metabolism are there?

A

3

32
Q

What is the most common and severe form of galactose metabolism?

A

Galactose-1-phosphate uridyl transferase deficiency

33
Q

What key feature to children galactose-1-phosphate uridyl transferase deficiency present with?

A

Conjugated hyperbilirubinaemia

34
Q

What complication can occur in children if galactose-1-phosphate uridyl transferase deficiency is not picked up on?

A

Bilateral cataracts

35
Q

How is mitochondrial DNA inherited?

A

Maternally

36
Q

What does heteroplasmy mean?

A

You need a certain load of mitochondrial DNA to develop symptoms

FS Chemical Pathology (26 decks)

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