What is galactosemia?

Causes and Symptoms

In classic I galactosemia, a congenital deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT) causes galactose to accumulate instead of being converted to glucose for energy production. As galactose accumulates in the child’s tissues and organs, it will have a toxic effect and cause various signs and symptoms. Galactosemia means “galactose in the blood.” Galactose is a sugar that may be found alone in foods but is usually associated with lactose, a milk sugar.

A gene mutation on the short arm of chromosome 9 has been identified in babies with galactosemia. About one in forty thousand newborns is affected with this autosomal recessive disorder. Both parents serve as carriers; they are not themselves affected, but each conception carries a one in four chance that the child will be born with galactosemia. Prenatal diagnosis is possible in cultured fibroblasts from amniotic fluid. Mandatory screening programs in many states test all newborns for galactosemia during the first week of life.

Galactosemia is an example of a multiple-allele system. In addition to the normal allele (G) and the recessive allele (g), a third allele, known as GD, has been found. The D allele is named after Duarte, California, where it was discovered. The existence of three alleles produces six possible genotypic combinations in the deoxyribonucleic acid (DNA). These enzymatic activities may range from 0 to 100 percent. Consequently, it is very important to monitor each patient with biochemical studies.

Homozygous recessive infants (gg) are unaffected at birth but develop symptoms a few days later, including jaundice, vomiting, an enlarged liver from extensive fatty deposits, cataracts, and failure to thrive. Mental retardation and death may also occur if dietary treatment has not been started.

Treatment and Therapy

Galactosemia is treated by removing foods that contain galactose from the diet. Since milk and milk products are the most common source of galactose, infants with galactosemia should not be given these foods. Serious problems can be prevented through this early exclusion of galactose.

While it is not possible for a child with galactosemia to have an entirely galactose-free diet, all persons with galactosemia should limit galactose intake from foods to a very low level. The galactose-1-phosphate levels determine the degree of dietary restriction for each individual. Advice from a dietician is needed.

Bibliography

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"Galactosemia." MedlinePlus, May 1, 2011.

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