Chem Path: Metabolic disorders and screening 1

Question 1

What happens in phenylketonuria (PKU)?

Answer 1

Phenylalanine hydroxylase deficiency that causes accumulation of phenylalanine, phenylpyruvate and phenylacetic acid (can be detected in urine).

Question 2

What is the effect of PKU in kids

Answer 2

Low IQ

Question 3

How soon does treatment for PKU have to be started

Answer 3

Within the first 6 weeks of life

Question 4

What is sensitivity of a test?

Answer 4

True positives / Total number with the disease

Question 5

What is specificity of a test?

Answer 5

True negatives / Total number withOUT the disease

Question 6

What is a positive predictive value

Answer 6

True positive / Total number with positive result

Question 7

What are some testing included in the Guthrie test?

Answer 7

Congenital hypothyroidism, sickle cell, cystic fibrosis, MCAD deficiency

Question 8

What happens in cystic fibrosis

Answer 8

Failure of CFTR which impedes movement of chloride ions, leading to increased Na and water which means you have thick viscous secretions

Question 9

How does Cf mutation detection work?

Answer 9

You have 4 common mutations, if you have 2 of them, you have a diagnosis of CF. If only 1 is present, you test for another 28 mutations.

Question 10

How does MCADD cause baby death?

Answer 10

You need to break down FFA so that they can get into mitochondria. The carnitine shuttle helps with this. In MCADD, you cannot produce acetyl CoA which is needed in the TCA cycle to spare glucose. So in between meals the baby becomes severely hypoglycaemic, leading to death.

Question 11

How is MCADD detected?

Answer 11

Measure C6-10 acylcarnitines using tandem mass spectometry

Question 12

What is homocystinuria?

Answer 12

Causes lens dislocation, mental retardation and thromboembolism