Genetic Fact Sheets for Parents

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Disorder Name:  Duarte galactosemia
Acronym:             DG deficiency

This fact sheet has general information about Duarte galactosemia (DG).  Many children with Duarte galactosemia never have any symptoms and there is no standard recommended treatment at this time. All children with Duarte galactosemia should be followed by a healthcare provider.

Classic galactosemia is a separate disorder from Duarte galactosemia. This factsheet is not intended to provide information about classic galactosemia. A factsheet on classic galactosemia can be found here.

What is Duarte galactosemia?

Duarte galactosemia is a specific type of galactosemia. Galactosemias are a group of rare inherited conditions. Galactosemia means “galactose in the blood.” People with Duarte galactosemia may or may not have problems digesting a type of sugar called galactose from the food they eat. Because they may not be able to break galactose down efficiently, it can build up in their blood. Galactose is found in milk and all foods that contain milk. However, many babies with newborn screening results showing Duarte galactosemia never have symptoms.

What causes Duarte galactosemia?

In order for the body to use different types of carbohydrates and sugars from the food we eat, special enzymes break them down into a smaller sugar called glucose, which the body uses for fuel.

Lactose, also called ‘milk sugar’ is the main type of sugar found in milk and milk products. It is made of one molecule of galactose and one molecule of glucose. Thus, all lactose, and all milk and milk products, contain galactose. During digestion, lactose is broken down to galactose and glucose. Then galactose is further changed by the body into glucose so it can be used as energy.

Duarte galactosemia occurs when an enzyme, called ‘galactose-1-phosphate uridyl transferase’ (GALT) is not working properly. This enzyme’s job is to change galactose into glucose. When the GALT enzyme is not working properly, galactose cannot be changed to glucose efficiently and galactose may build up in the blood. The decision of whether or not to treat someone with Duarte galactosemia depends in part on the level of galactose in the blood.

Types of Galactosemia
There are different types of galactosemia. Classic galactosemia is a rare, serious, life-threatening disorder. Duarte galactosemia, while more common, is far less severe. Duarte galactosemia has not been well studied. Many individuals with Duarte galactosemia never develop any symptoms due to this condition.

Classic galactosemia
Classic galactosemia occurs when babies have no or very small amounts of the GALT enzyme. Babies start showing health effects within days of feeding on breast milk or milk-containing formulas. Virtually all cases of classic galactosemia can be detected by newborn screening. This factsheet provides more information on classic galactosemia.

Duarte galactosemia
Duarte galactosemia is a more common form of galactosemia that is often, but not always, detected during newborn screening. Duarte galactosemia occurs when babies have smaller amounts of and less efficient forms of the GALT enzyme. Some children with this condition have problems breaking down galactose from the food they eat. Babies with Duarte galactosemia may need less treatment or no treatment at all. DNA testing, described below, and other blood tests can help determine if your baby has classic or Duarte galactosemia.

Galactosemia diagram

If Duarte galactosemia is not treated, what problems occur?

Most children with Duarte galactosemia have no symptoms at all and may not need treatment. Children with Duarte galactosemia that do need treatment but do not receive it may develop jaundice in the newborn period. Studies are conflicting as to whether children with Duarte galactosemia have long-term effects from elevated galactose levels in the first year of life. Research is ongoing to determine if there are any long-term effects associated with non-treatment of individuals with Duarte galactosemia. These possible long-term effects may include specific learning differences but not intellectual differences. Girls with Duarte galactosemia are not known to have premature ovarian failure which can be seen in girls with classic galactosemia.

What is the treatment for Duarte galactosemia?

Your baby’s primary doctor will work with a metabolic doctor and a dietitian familiar with Duarte galactosemia to care for your child. Children with mild Duarte galactosemia may or may not need treatment. Babies and young children with Duarte galactosemia may need regular blood and urine tests. The test results will help your doctors and dietitian determine if treatment is necessary. Your metabolic doctor and dietitian will let you know if your child needs to avoid lactose and galactose. If so, they will give you a special food plan designed to keep your child healthy.

Treatment, if needed, consists of the use of a special lactose-free formula and/or a lactose and galactose free diet. The special food plan, if used, is only during the first year of life because children with Duarte galactosemia develop an increased tolerance for dietary galactose as they grow.

What happens when Duarte galactosemia is treated?

Because most individuals with Duarte galactosemia never develop symptoms because of this condition, it is unclear if there is a benefit to early treatment. Children with Duarte galactosemia, regardless of whether they are treated or not, are able to live healthy lives with typical growth and development.

What causes the GALT enzyme to be absent or not working correctly?

Genes tell the body to make various enzymes. People with Duarte galactosemia have a pair of genes that do not work correctly. Because of the changes in this pair of genes, the GALT enzyme either does not work properly or efficiently.

How is Duarte galactosemia inherited?

Duarte galactosemia is inherited in an autosomal recessive manner. It affects both boys and girls equally. 

Everyone has a pair of genes that make the GALT enzyme. In children with Duarte galactosemia, neither of these genes works correctly. There are two types of non-working genes in Duarte galactosemia. One is a very mild mutation called “D” for “Duarte variant”. The other is called “G” and is a more severe mutation. A child with Duarte galactosemia has either D/D copies of the gene or D/G.

These children inherit one non-working gene for the condition from each parent.

Parents of children with Duarte galactosemia rarely have the condition themselves. Instead, each parent has a single non-working gene for Duarte galactosemia. They are called carriers. Carriers do not have Duarte galactosemia because the other gene of this pair is working correctly. Without testing the parents, it is not possible to know which variant, D or G, each parent carries.

When both parents are carriers, there is a 25% chance in each pregnancy for the child to have Duarte galactosemia. There is a 50% chance for the child to be a carrier, just like the parents. And, there is a 25% chance for the child to have two working genes.

Autosomal Recessive Inheritance Chart

Genetic counseling is available to families who have children with Duarte galactosemia. Genetic counselors can answer your questions about how Duarte galactosemia is inherited, choices during future pregnancies, and how to test other family members. Ask your doctor about a referral to a genetic counselor.

Is genetic testing available?

Genetic testing for Duarte galactosemia can be done on a blood sample. Genetic testing, also called DNA testing, looks for changes in the pair of genes that causes Duarte galactosemia. Over 99% of the time, DNA testing can identify both gene changes in a child with this condition.

DNA testing is not necessary to diagnose your child. However, it may be helpful in determining what type of Duarte galactosemia your child has. Children with D/G gene changes sometimes need treatment. Children with D/D gene changes usually do not need treatment.

DNA testing can also be helpful for carrier or prenatal testing, discussed below.

What other testing is available?

If your child has had a positive screen for Duarte galactosemia through a newborn screening program, other tests still need to be done in order to confirm the diagnosis. One of these special tests detects the amount of GALT enzyme present in red blood cells and is often used to confirm Duarte galactosemia.

Other blood or urine tests may be helpful to determine whether your child needs treatment or whether treatment is working properly. Ask your doctor if you have any questions about testing for Duarte galactosemia.

Can you test during pregnancy?

If both gene changes have been found in your child with Duarte galactosemia, DNA testing can be done during any future pregnancies. The sample needed for this test is obtained by either CVS or amniocentesis.

Parents may choose to have testing during pregnancy or wait until birth to have the baby tested. A genetic counselor can talk to you about your choices and answer questions about prenatal testing or testing your baby after birth.

Can other members of the family have Duarte galactosemia or be carriers?

Having Duarte galactosemia
The brothers and sisters of a baby with Duarte galactosemia have a chance of being affected. Ask your metabolic doctor whether your other children should be tested.

Duarte galactosemia carriers
Brothers and sisters who do not have Duarte galactosemia still have a 2/3rds chance to be carriers like their parents. Except in special cases, carrier testing should only be done in people over 18 years of age.

Each of the parents’ brothers and sisters has a 50% chance to be a carrier. It is important for other family members to be told that they could be carriers. There is a small chance they are also at risk to have children with galactosemia or Duarte galactosemia depending on which gene change they carry.

All 50 US states offer newborn screening for classic galactosemia. Newborns with Duarte variant galactosemia may or may not be detected by the same newborn screening test that detects classic galactosemia. Specifically, some newborn screening protocols are designed to detect Duarte variant galactosemia, while others do not. In families in which a child has Duarte galactosemia, newborn screening results are not sufficient to rule out this condition in future siblings.

Can other family members be tested?

Diagnostic testing
If there is concern about whether they have Duarte galactosemia, your other children can be tested. Talk to your doctor or genetic counselor if you have questions about testing for Duarte galactosemia.

Carrier testing
If both gene changes have been found in your child, other adult family members can have DNA testing to see if they are carriers.

If DNA testing is not helpful, other methods of carrier testing may be available. If you have questions about carrier testing, ask your genetic counselor or metabolic doctor.

How many people have Duarte galactosemia?

About one in every 3,000 to 6,000 babies in the United States is born with Duarte galactosemia.

Does Duarte galactosemia happen more often in a certain ethnic group?

Duarte galactosemia occurs in people of all ethnic groups around the world.

Does Duarte galactosemia go by any other names?

Duarte galactosemia is sometimes also called:

Variants of classic GALT that are not discussed in depth in this fact sheet include:

Where can I find more information?

Duarte Galactosemia
http://www.Duartegalactosemia.org

Baby’s First Test
http://www.babysfirsttest.org

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DISCLAIMER:

THIS INFORMATION DOES NOT PROVIDE MEDICAL ADVICE. All content ("Content"), including text, graphics, images and information are for general informational purposes only. You are encouraged to confer with your doctor or other health care professional with regard to information contained on this information sheet. After reading this information sheet, you are encouraged to review the information carefully with your doctor or other healthcare provider. The Content is not intended to be a substitute for professional medical advice, diagnosis or treatment. NEVER DISREGARD PROFESSIONAL MEDICAL ADVICE, OR DELAY IN SEEKING IT, BECAUSE OF SOMETHING YOU HAVE READ ON THIS INFORMATION SHEET. This project is supported by a grant from the Maternal and Child Health Bureau, Health Resources and Service Administration, Genetic Services Branch, MCH Project #:H46MC24091 http://mchb.hrsa.gov

Fact Sheet was last updated on: 5/5/2017