Topic overview

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Lactase in the intestinal brush border splits lactose into glucose and galactose. Galactokinase then uses ATP to form galactose-1-phosphate, and GALT transfers this intermediate into reactions involving UDP-galactose and glucose-1-phosphate. UDP-galactose 4-epimerase interconverts UDP-galactose and UDP-glucose. When galactose accumulates, an alternate pathway can produce galactitol, which may contribute to lens injury. Classic galactosemia results from GALT deficiency and can present in neonates with feeding-related illness, jaundice, liver enlargement, cataracts, or sepsis. Galactokinase deficiency is generally milder, while epimerase deficiency varies in severity. The topic also introduces diagnostic clues and newborn screening, dietary management, monitoring, and complications that may occur if the condition is untreated.