metabolic disorders

Question 1

Testing for congenital hypothyroidism

Answer 1

• Increased TSH

Question 2

Testing for cystic fibrosis

Answer 2

• Increased immune reactive trypsinogen
• If this is raised, test for mutations (panel of 4)

2 mutations identified - diagnostic
1 mutation identified - expand the panel to 28 mutation, still need 2 for diagnosis
0 mutations identified - repeat IRT in 21-28 days

Question 3

Testing for MCADD

Answer 3

acytylcarnitine levels

via mass tandem spectometry

Question 4

Testing for PKU

Answer 4

Blood phenylalanine

Question 5

Hyperammonaemia

Answer 5

VOMITING
RESPIRATORY ALKALOSIS
NEUROLOGICAL CHANGES

Ix

• plasma glutamine
• plasma amino acids
• urine orotic acid

Question 6

Organic aciduria

Answer 6

HYPERAMMONAEMIA
METABOLIC ACIDOSIS
HIGH ANION GAP

• Strange-smelling urine
• Truncal hypotonia, with limb hypertonia

Question 7

Isovalaeric aciduria

Answer 7

• Deficiency of isovaleric dehydrogenase
• Isovaleric coA accumulates
• Excreted in urine

Question 8

Mitochondrial fatty acid Beta oxidation

Answer 8

HYPOKETOTIC HYPOLYCAEMIA
HEPATOMEGALY
CARDIOMYOPATHY

Ix

• Blood ketones
• Urine organic acids
• Blood spot acycarnitine

Question 9

Galactosaemia

Answer 9

VOMITING + DIARRHOEA
CONJUGATED HYPERBILIRUBINAEMIA 
HEPATOMEGALY
HYPOGLYCAEMIA
SEPSIS 

Ix

• RBC GAL-1-PUT
• Urine galactose (high)

Tx - galactose-free diet

Risks - bilateral cataracts

Question 10

Characteristic findings in mitochondrial disorders

Answer 10

Raised lactate + Raised CK