Galactose epimerase deficiency


Galactose epimerase deficiency, also known as GALE deficiency, Galactosemia III and UDP-galactose-4-epimerase deficiency,[1] is a rare form of galactosemia associated with a deficiency of the enzyme galactose epimerase.


* Developmental delay * Motor retardation * Language retardation * Learning difficulties * Concentration difficulties


Both forms of galactosemia are inherited as autosomal recessive defects and occur in about 1 in 60,000 births in the United States. Up to 1.25% of the population is heterozygous for the classic galactosemia gene. Classic galactosemia results from a defect in the enzyme galactose-1-phosphate uridyl transferase. (See Metabolic pathway in galactosemia.) Galactokinase-deficiency galactosemia, the rarer form of this disorder, stems from a deficiency of the enzyme galactokinase. In both forms of galactosemia, the inability to normally metabolize the sugar galactose (which is mainly formed by digestion of the disaccharide lactose that’s present in milk) causes galactose accumulation.


Inherited deficiencies of galactose epimerase are detected by the finding of elevated galactose sugars in newborn screening programs designed to detect classic galactosemia but with normal levels of galactose-1-phosphate uridylyltransferase. Most of the mild cases have deficiency in red cells and uncultured white blood cells with presence of the enzyme in liver and cultured skin fibroblasts


Although a galactose-free diet is recommended in galactokinase deficiency and in classic galactosemia, patients with galactose epimerase deficiency cannot utilize the endogenous pathway for synthesis of UDP-galactose, making them dependent on exogenous galactose; thus, a galactose-restricted rather than a galactose-free diet is recommended in the management of this disorder . The clear dual function of this enzyme suggests that dietary supplements with both galactose and N-acetylgalactosamine should be considered for galactose epimerase-deficient patients .