What is galactosemia?

Galactosemia is a rare genetic disorder. People with this disorder are missing an enzyme called galactose-1-phosphate uridyl transferase or Gal-1-PUT. This enzyme has a job. It is supposed to break down galactose in the body. Galactose is a sugar. The body gets most of its galactose from the breakdown of lactose, which is the main sugar in milk. Galactose is supposed to be broken down further into another sugar called glucose (which is a main energy source for the body) and other molecules essential for the proper function of the body. Because people with galactosemia are missing an enzyme, galactose cannot be broken down and instead ends up building up in the body. When galactose builds up, it becomes toxic to the cells. The name, galactosemia, means 'too much galactose in the blood.' If not identified and treated promptly, life-threatening complications can occur. Most infants with galactosemia are diagnosed through newborn screening and put on a lactose-restricted diet within the first 10 days of life. Despite early recognition and prompt treatment, infants and children with galactosemia remain at risk for delays in reaching developmental milestones, speech delays, or problems with motor function. Changes (mutations) to the GALT gene cause classic galactosemia.

In addition to classic galactosemia, some individuals have clinical variant galactosemia. It is caused by different mutations to the GALT gene and has the same signs and symptoms as classic galactosemia. Another form of galactosemia is called Duarte variant galactosemia. The Duarte form has not been shown to cause any signs or symptoms, and many doctors do not consider it a real disease. However, adequate studies to confirm this have not been done and there have been anecdotal reports of mild symptoms in some people.

Berry GT. Classic Galactosemia and Clinical Variant Galactosemia. GeneReviews website. Accessed November 4, 2016.

Galactosemia. Genetics Home Reference website. Accessed November 4, 2016.

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