Galactosemia

What is galactosemia?

Galactosemia is a disorder that affects how the body processes certain sugars (sugar metabolism). This condition results when the body is not able to process the sugar galactose, which is found in many foods. Galactose also exists as part of another sugar, lactose, found in all dairy products. Liver dysfunction, cataracts (clouding of the lens of the eye), speech problems, and mental impairment are characteristic of this condition if not treated.

How common is galactosemia?

Classic galactosemia is an inherited disorder that occurs in approximately 1 in 30,000 live births. The incidence of the Duarte variant, a mild type of galactosemia, is more common. This variant affects an estimated 1 in 16,000 live births.

What genes are related to galactosemia?

Mutations in the GALE, GALK1, and GALT genes cause galactosemia.

Most cases of galactosemia are categorized as classic, or type I, galactosemia and are caused by mutations in the GALT gene. This gene produces the enzyme galactose-1-phosphate uridyl-transferase, which is important in processing galactose. Mutations in the GALT gene cause two forms of type I galactosemia, classic and Duarte variant. Individuals with the classic type of galactosemia lack nearly all the enzyme activity necessary to metabolize galactose. Individuals with the Duarte variant have approximately 5 to 20 percent of the enzyme activity necessary to metabolize this sugar and often do not have signs or symptoms of galactosemia.

Galactosemia type II results from mutations in the GALK1 gene, which cause a shortage of the enzyme galactokinase. Galactosemia type III results from mutations in the GALE gene, which cause a shortage of the enzyme UDP-galactose-4-epimerase. Both of these enzymes also play a role in the proper metabolism of galactose.

How do people inherit galactosemia?

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.

Galactosemia on Wikipedia

'''Galactosemia''' is a rare genetic Metabolism Disease which affects an individual's ability to properly Digestion the sugar galactose. Lactose in food (such as dairy products) is broken down by the body into glucose and galactose. Normally, galactose is then converted into glucose by the enzyme GALT (galactose-1-phosphate uridylyltransferase). In individuals with galactosemia, GALT activity is severely diminished, leading to toxic levels of galactose to build up in the blood, resulting in hepatomegaly (an enlarged liver), renal failure, cataracts, and brain damage. Without treatment, mortality in infants with galactosemia is about 75%. Goppert first described the disease in 1917. Its incidence is about 1 per 47,000 births (classic type). It is much rarer in Japan.

Types

There are two variants of the gene responsible for galactosemia. One variant causes so-called '''classic galactosemia''', in which GALT activity is nearly zero and the most serious symptoms of galactosemia are prominent. The variant gene, responsible for '''Duarte galactosemia''', leads to about half the normal levels of GALT. Individuals with Duarte galactosemia may experience few or none of the serious symptoms of classic galactosemia. The severity of the symptoms is dependent on a number of factors, most importantly the amount of lactose in the individual's diet (nutrition). It is also possible to have one each of the classic and Duarte genes, in which case GALT activity is intermediate.

Diagnosis

Infants are now routinely screened for galactosemia in the United States, and diagnoses are often made early.

Treatment

The only treatment for classic galactosemia is eliminating lactose and galactose from the diet. Even with an early diagnosis and a restricted diet, however, some individuals with galactosemia experience long-term complications such as learning disability, and in girls, ... [ Read More ]

External Resources

Parents of Galactosemic Children, Inc. - Information about galctosemia and a resource for families living with galactosemia.

NORD - Galactosemia - Offers the synonyms, a general discussion and further resources.

MedlinePlus: Galactosemia - Includes symptoms, tests, treatment, and prevention.

Pediatric Oncall - Presented is a case study of galactosemia in a four month old female child.