Phenylketonuria

Question 1

Phenylketonuria (PKU) is a rare genetic disorder that leads to elevated levels of what in the blood?

1 - ketones
2 - lactic acid
3 - urea
4 - phenylalanine

Answer 1

4 - phenylalanine

Question 2

What is the incidence of Phenylketonuria (PKU)?

1 - 1/100
2 - 1/1000
3 - 1/10,000
4 - 1/100,000

Answer 2

3 - 1/10,000

Question 3

Phenylketonuria is a rare genetic disorder that leads to elevated levels of phenylalanine in the blood. What can this condition then lead to?

1 - CHF
2 - CKD
3 - respiratory distress syndrome
4 - severe brain disorders

Answer 3

4 - severe brain disorders

Question 4

Phenylalanine is an amino acid. Is this an essential or non-essential amino acid?

Answer 4

• essential amino acid, meaning the body needs to consume food to get the amino acids
• non-essential means the body can make it

Question 5

Once phenylalanine is consumed in food, such as proteins, what is the majority of it converted into?

1 - tyrosine
2 - tropheryma
3 - tryptophan
4 - theanine

Answer 5

1 - tyrosine
- enzyme phenylalanine hydroxylase converts it

Question 6

Once phenylalanine is consumed in food, such as proteins, the majority of phenylalanine is converted into tyrosine. Tyrosine is then used to make all of the following EXCEPT which one?

1 - dopamine
2 - noradrenaline
3 - adrenaline
4 - thyroid hormone
5 - cortisol

Answer 6

5 - cortisol

Question 7

Phenylketonuria (PKU) is a rare genetic disorder that leads to elevated levels of phenylalanine in the blood. This is an inborn genetic disorder. How is this transmitted?

1 - autosomal dominant
2 - autosomal recessive
3 - X-lined recessive
4 - X-linked dominant

Answer 7

2 - autosomal recessive
- need the mutated gene from each parent, otherwise you are just a carrier

Question 8

Phenylketonuria (PKU) is a rare autosomal recessive disorder that leads to elevated levels of phenylalanine in the blood. What is the mutation that causes PKU?

1 - alpha-1 antitrypsin deficiency.
2 - THTR1 absorption in GIT
3 - phenylalanine hydroxylase
4 - all of the above

Answer 8

3 - phenylalanine hydroxylase
- located on chromosome 12
- over 600 mutations

Question 9

Phenylketonuria (PKU) is a rare autosomal recessive disorder that leads to elevated levels of phenylalanine in the blood due to a mutation in the enzyme phenylalanine hydroxylase. The activity of the enzyme can vary, but what are the most common signs patients can present with?

1 - blonde hair
2 - blue eyes
3 - neuropsychological problems
4 - low IQ
5 - impaired myelination
6 - seizures
7 - all of the above

Answer 9

7 - all of the above

• high PKU means high melanin, which is responsible for blond hair and blue eyes
• high PKU can also cause low myelination

Question 10

If a woman is pregnant has Phenylketonuria (PKU), she must monitor her PKU levels carefully. In a foetus if the women has PKU syndrome, they can develop all of the following EXCEPT which one?

1 - heart defects
2 - severe mental disability
3 - microcephaly
4 - spina bifida

Answer 10

4 - spina bifida
- not common in PKU

Question 11

Phenylketonuria (PKU) is a rare autosomal recessive disorder that leads to elevated levels of phenylalanine in the blood due to a mutation in the enzyme phenylalanine hydroxylase. The elevated levels of PKU are able to enter the brain. How is this possible?

1 - fat soluble so can diffuse across BBB
2 - bind to CO2 and diffuse across BBB
3 - use same transporter as tyrosine to cross BBB
4 - all of the above

Answer 11

3 - use same transporter as tyrosine to cross BBB

Question 12

Phenylketonuria (PKU) is able to enter the brain as it used the same transporter as tyrosine to cross BBB. However, PKU can also block all the transports across the BBB due their high levels. Which 2 amino acids does this then significantly reduce in the brain?

1 - trptophan
2 - argaine
3 - serine
4 - tyrosine

Answer 12

1 - trptophan
4 - tyrosine

Question 13

What neurotransmitter needs tryptophan for its synthesis?

1 - dopamine
2 - noradrenaline
3 - adrenaline
4 - serotonin

Answer 13

4 - serotonin

Question 14

All the following neurotransmitter need tyrosine for its synthesis, EXCEPT which one?

1 - dopamine
2 - noradrenaline
3 - glutamate
4 - adrenaline

Answer 14

3 - glutamate

Question 15

Phenylketonuria (PKU) is a rare autosomal recessive disorder that leads to elevated levels of phenylalanine in the blood due to a mutation in the enzyme phenylalanine hydroxylase. High levels of PKU can block amino acids from entering the brain, tryptophan and tyrosine. This can lead to neurodevelopment issues due to low levels of which 3 of the following neurotransmitters?

1 - serotonin
2 - glutamate
3 - noradrenaline
4 - dopamine

Answer 15

1 - serotonin
3 - noradrenaline
4 - dopamine

Question 16

Typically what is the first line test to diagnose Phenylketonuria (PKU)?

1 - PCR
2 - amniocentesis
3 - heel prick test
4 - ultrasound

Answer 16

3 - heel prick test
- blood levels of phenylalanine (>120 uM) and tyrosine are measured
- if phenylalanine is higher than tyrosine, further testing is performed to confirm amino acid levels

Question 17

How can we reduce levels of phenylketonuria (PKU) in the blood?

1 - reduce food intake containing PKU
2 - supplement other amino acids
3 - tetrahydrobiopterin a co-factor used to degrade PKU
4 - all of the above

Answer 17

4 - all of the above

Question 18

Why should diet drinks be restricted in phenylketonuria (PKU)?

1 - contain a lot of Na+ than can exacerbate neuro symptoms
2 - contains a lot of aspartame
3 - contains a lot of fake sugar which can increase PKU absorption
4 - all of the above

Answer 18

2 - contains a lot of aspartame
- aspartame = aspartic acid, methanol and phenylalanine
- so lots of soft drinks makes PKU worse