Differential Diagnosis: Galactokinase (GALK) deficiency; UDP-galactose-4 epimerase deficiency; undefined increase.
Condition Description: Galactose comes from the lactose of breast milk or formula. Galactokinase deficiency is caused by a defect in conversion of galactose to galactose-1-phosphate. Epimerase deficiency limits the production of UDP-galactose, a co-substrate of GALT.
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The diagnosis of galactokinase and epimerase deficiencies is established by quantitation of the respective enzyme activity in erythrocytes.
The neonate is usually normal. If GALK deficiency is untreated, cataracts develop. Treatment is withdrawal of milk. Epimerase deficiency is usually benign.