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Leila's Yr 5 Pathology (COPY) > Chem path 5s - Metabolic disorders 1 > Flashcards

Chem path 5s - Metabolic disorders 1 Flashcards

1
Q

What is the most common pattern of metabolic disease inheritance?

A

Autosomal

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2
Q

What are the three types of inherited disorders?

A

Chromosomal, polygenic, monogenic

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3
Q

deficient enzyme activity can lead to biochemical hallmarks of the metabolic disorder. What are these?

A

Lack of end product
Build up of pre-cursors
Abnormal, often toxic metabolites (due to large amount of substrate that does not usually react with the enzyme, start reacting)

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4
Q

What is the deficiency in phenylketonuria?

A

Phenylalanine hydroxylase

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5
Q

What does phenylalanine hydroxylase do?

A

Converts phenylalanine in to tyrosine

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6
Q

If deficient in PAH, what biocehmical changes are seen?

A

Build up of phenylalanine (toxic)

Abnormal metabolites: phenylpyruvate and phenylacetic acid

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7
Q

Where is phenylacetic acid detected?

A

In the urine

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8
Q

What is the prevalence of pKU?

A

1 in 5,000 (common)

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9
Q

What are the key features of PKU?

A 
Low IQ (<50)
Musty odour
Behavioural issues
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10
Q

What is the test for PKU?

A

Check serum for phenylalanine

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11
Q

What is the management of PKU?

A

Phenylalanine dietary restriction, management has to be started within the FIRST 6-WEEKS OF LIFE

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12
Q

What is sensitivity?

A

The number of true positives/ total number with the disease (Fraction)

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13
Q

What is specificity?

A

The true negatives / total number without the disease

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14
Q

What is +ve predictive value?

A

True positives/ total number with positive RESULT

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15
Q

What is -ve predictive value?

A

True negatives / total number with negative RESULT

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16
Q

What tends to be prioritised in IMDs?

A

sensitivity as do NOT want to miss a diagnosis

17
Q

When is the Guthrie screen performed?

A

Days 5-8 of life

18
Q

On the Guthrie card, what is the diagnosis of congenital hypothyroidism based on?

A

High TSH

19
Q

How many classes of cystic fibrosis are there?

A

6

20
Q

What is CF caused by?

A

Failure of the cystic fibrosis transmembrane conductance regulator (CFTR) which leads to the inability of chloride ions in the epithelial cells to move out in to the lumen, increased Na+/Water reabsorption –> viscous secretions –> duct blockage

21
Q

What is the screening test for CF?

A

High immune reactive trypsinogen (IRT)

22
Q

What is the most common CF mutation?

A

DF508

23
Q

How do you interpret CF screening (IRT) results?

A

If the IRT >99.5th centile in 3 blood spots –> mutation detections
There are 4 very common mutations. If you get 2/4 mutations then a diagnosis of CF is confirmed. If you get 1/4 mutations, the panel is extended to 28 mutations. If youget 0/4 mutations, you do another IRT at 21-28 days.

24
Q

What kind of disorder is MCADD?

A

Fatty acid oxidation disorder

25
Q

If you are deficient in MCAD, what will happen?

A

No production of acetyl-CoA from fatty acids. Acetyl-CoA is used in the TCA cycle to produce ketones, which spares glucose (brain dependent on glucose metabolism) . You use fat when you are fasting or between meals, in order to spare your glucose stores.

26
Q

What does MCADD classically cause in infants?

A

Cot death. If a baby cannot break down fats then when they are not feeding they will get massively hypoglycaemic and die.

27
Q

How is MCADD screened for?

A

Measuring C6-C10 acylcarnitine using tanden mass spectrometry

28
Q

How do you treat MCADD?

A

make sure the child NEVER becomes hypoglycaemic, and hence never becomes reliant on fats for energy

29
Q

What is the defect in homocystinuria?

A

There is a failure of remethylation of homocysteine

30
Q

What are the clinical features of homocystinuria?

A

Lens dislocation
Mental retardation
Thromboembolism
Brittle hair/ fair skin

31
Q

Which nine disorders are currently screened for using the Guthrie screen?

A 
PKU
Congenital hypothyroidism
CF
MCADD
SCD
Maple syrup urine disease
Isovaleric acidaemia
Glutaric aciduria type I
LCADD

Leila's Yr 5 Pathology (COPY) (100 decks)

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