Disorders of Galactose Metabolism

Galactokinase deficiency

  • 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).

Classic galactosemia

  • 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.

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