Chem path

Question 1

Test for Vitamin B1 (Thiamine) deficiency

Answer 1

Red blood cell transketolase

Question 2

Enzyme missing in Acute Intermittent porphyria

Answer 2

Porphobilinogen (PBG) deaminase

Question 3

Vitamin deficiency leading to Casal’s necklace

Answer 3

Vitamin B3 (niacin)

Question 4

Sweet odour + sweaty feet in infant

Answer 4

Maple syrup urine disease

Maple syrup urine disease (C) is an organic aciduria, a group of disorders
that represent impaired metabolism of leucine, isoleucine and
valine. As a result, toxic compounds accumulate causing toxic encephalopathy
which manifests as lethargy, poor feeding, hypotonia and/or
seizures. Characteristic of maple syrup urine disease are a sweet odour
and sweaty feet. The gold standard diagnostic test is gas chromatography
with mass spectrometry. Management involves the avoidance of
the causative amino acids.

Question 5

‘Cherry-red spot’ on infant

Answer 5

Fabry’s disease

Fabry’s disease (F) is a lysosomal storage disorder in which there is
deficiency in α-galactosidase. Presentation is almost always a child
with developmental delay together with dysmorphia. Other findings
may involve movement abnormalities, seizures, deafness and/or blindness.
On examination, hepatosplenomegaly, pulmonary and cardiac
problems may be noted. The pathognomonic feature of lysosomal storage
disorders is the presence of a ‘cherry-red spot’.

Question 6

‘floppy’ baby + hypoglycaemia + heptomegaly + enlarged kidneys

Answer 6

Von Gierke’s disease

Von Gierke’s disease (E) is one of nine glycogen storage disorders, in
which a defect in the enzyme glucose-6-phosphate results in a failure
of mobilization of glucose from glycogen. The metabolic disease
presents in infancy with hypoglycaemia. The liver is usually significantly
enlarged and kidney enlargement can also occur. Other glycogen
storage disorders (and enzyme defects) include Pompe’s (lysosomal
α-glucosidase), Cori’s (amylo-1,6-glucosidase) and McArdle’s (phosphorylase);
each disorder presents with varying degrees of liver and
muscle dysfunction.