Galactosemia is an inborn error of
galactose metabolism that occurs mainly as the outcome of
galactose-1-phosphate uridyltransferase (GALT)
deficiency. The
ability to assess
galactose oxidation following
administration of a
galactose-labeled
isotope (1-13C-
galactose) allows the
determination of
galactose metabolism in a practical manner. We aimed to assess the level of
galactose oxidation in both healthy and galactosemic Brazilian
children. Twenty-one healthy
children and seven
children with
galactosemia ranging from 1 to 7 years of age were studied. A
breath test was used to quantitate 13CO2 enrichment in exhaled
air before and at 30, 60, and 120 min after the
oral administration of 7 mg/kg of an aqueous
solution of 1-13C-
galactose to all
children. The
molar ratios of 13CO2 and 12CO2 were quantified by the mass/
charge ratio (m/z) of stable
isotopes in each
air sample by gas-
isotope-ratio
mass spectrometry. In sick
children, the cumulative percentage of 13C from labeled
galactose (CUMPCD) in the exhaled
air ranged from 0.03% at 30 min to 1.67% at 120 min. In contrast,
healthy subjects showed a much broader range in CUMPCD, with values from 0.4% at 30 min to 5.58% at 120 min. The study found a significant difference in
galactose oxidation between
children with and without
galactosemia, demonstrating that the
breath test is useful in discriminating
children with
GALT deficiencies.