Classical galactosaemia is the more severe disease and arises from deficiency of galactose 1-phosphate uridyl transferase. Affected patients excrete excess galactose in the urine and also accumulate galactose and galactose 1-phosphate in the blood. There is an early neonatal presentation with failure to thrive, vomiting and liver disease, but these early signs are reversed when the baby is placed on a galactose-free diet. The incidence is about 1 in 70,000. Galactokinase deficiency galactosaemia is a much rarer disease than classical galactosaemia, and the only consistent clinical features are cataracts, occurring either before or just after birth. It is possible that heterozygotes for the condition develop cataracts in later life, and the laboratory is sometimes asked to test adults for intermediate activity.
Enzyme Tests: Classical galactosaemia is tested for by measuring blood levels of galactose 1-phosphate uridyl transferase. Galactokinase deficiency galactosaemia is tested for by measuring blood levels of galactokinase.