MSD Manual

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Matt Demczko

, MD, Mitochondrial Medicine, Children's Hospital of Philadelphia

Reviewed/Revised Dec 2021 | Modified Sep 2022

Galactosemia (a high blood level of galactose) is a carbohydrate metabolism disorder Overview of Carbohydrate Metabolism Disorders Carbohydrate metabolism disorders are hereditary metabolic disorders. Hereditary disorders occur when parents pass the defective genes that cause these disorders on to their children. There... read more that is caused by a lack of one of the enzymes necessary for metabolizing galactose, a sugar that is part of a larger sugar called lactose (milk sugar). A metabolite that is toxic to the liver and kidneys builds up. The metabolite also damages the lens of the eye, causing cataracts. Galactosemia occurs when parents pass a defective gene Genes Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body or the code for functional ribonucleic... read more Genes that causes this disorder on to their children.

  • Galactosemia is caused by a lack of one of the enzymes needed to metabolize the sugar in milk.

  • Symptoms include vomiting, jaundice, diarrhea, and abnormal growth.

  • The diagnosis is based on blood and urine tests.

  • Even with adequate treatment, affected children still develop mental and physical problems.

  • Treatment involves completely eliminating milk and milk products from the diet.

Galactose is a sugar that is present in milk as part of lactose and in some fruits and vegetables. Deficiency of a certain enzyme can alter the breaking down (metabolizing) of galactose, which can lead to high levels of galactose in the blood (galactosemia). There are different forms of galactosemia, but the most common and the most severe form is referred to as classic galactosemia.

Symptoms of Galactosemia

Newborns with galactosemia seem normal at first but, within a few days or weeks of consuming breast milk or lactose-containing formula, lose their appetite, vomit, become jaundiced (yellow skin and eyes—see Jaundice in the Newborn Jaundice in the Newborn Jaundice is a yellow color to the skin and/or eyes caused by an increase in bilirubin in the bloodstream. Bilirubin is a yellow substance formed when hemoglobin (the part of red blood cells... read more Jaundice in the Newborn ), have diarrhea, and stop growing normally. White blood cell function is affected, and serious infections can develop.

Many children also have cataracts. Girls often have ovaries that do not function, and only a few are able to conceive naturally. Boys, however, have normal testicular function.

Diagnosis of Galactosemia

  • Blood and urine tests

Galactosemia is detectable with a blood test. This test is done as a routine screening test for newborns Newborn Screening Tests Screening tests are done to detect health conditions that are not yet causing symptoms. Many serious disorders that are not apparent at birth can be detected by various screening tests. Early... read more in all states in the United States. Before conception, adults with a sibling or child known to have the disorder can be tested to find out whether they carry the gene that causes the disease. If two carriers conceive a child, that child has a 1 in 4 chance of being born with the disease. Carriers Carrier Screening Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more are people who have an abnormal gene for a disorder but who do not have symptoms or visible evidence of the disorder.

Another test is done to look for elevated levels of galactose in the urine.

Prognosis for Galactosemia

If galactosemia is recognized at birth and adequately treated, liver and kidney problems do not develop, and initial mental development is normal. However, even with adequate treatment, children with galactosemia may have a lower intelligence quotient (IQ) than their siblings, and they often develop speech and balance problems during adolescence.

Treatment of Galactosemia

  • Elimination of galactose from the diet

Galactosemia is treated by completely eliminating milk and milk products—the main source of galactose—from an affected child’s diet. Because galactose is present in both human breast milk and cow's milk–based infant formulas, infants are typically fed a soy-based infant formula after diagnosis. People who have the disorder must restrict galactose intake throughout life. Galactose is also present to a much lesser extent in some fruits, vegetables, and sea products, such as seaweed, but doctors have not found that it helps people to avoid these foods. It is also used as a sweetener in many foods. Many people need to take calcium and vitamin supplements.

More Information

The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

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