- Hereditary deficiency of galactokinase. Galactitol accumulates if galactose is present in diet. Relatively mild condition. Autosomal recessive.
- Symptoms: galactose appears in blood (galactosemia) and urine (galactosuria); infantile cataracts. May present as failure to track objects or to develop a social smile. Galactokinase deficiency is kinder (benign condition).
- Absence of galactose-1-phosphate uridyltransferase. Autosomal recessive. Milder version – partial transferase deficiency.
- Damage is caused by accumulation of toxic substances (including galactitol, which accumulates in the lens of the eye).
- Symptoms develop when infant begins feeding (lactose present in breast milk and routine formula)
- Failure to thrive, feeding intolerance
- Jaundice, hepatomegaly
- Infantile cataracts
- Renal damage
- Intellectual disability, lethargy, hypotonia, convulsions
- Can predispose to E coli sepsis in neonates.
- Long-term sequelae (even with treatment): ovarian failure, developmental delay, learning disability
- Treatment: exclude galactose and lactose (galactose + glucose) from diet.
Galactose-4-epimerase deficiency (GALE)
- Benign form – healthy individuals. Enzyme deficiency limited to leukocytes & erythrocytes
- Severe form – similar to transferase deficiency
Fructose is to Aldolase B as Galactose is to UridylTransferase (FAB GUT).
The more serious defect (hereditary fructose intolerance & galactosemia) leads to PO43− depletion.