General Condition Information
- Classical galactosemia
- Galactosemia (Classical)
- Transferase deficient galactosemia (classical)
- It is estimated that less than 90 babies are born with this condition each year in the United States.
- Visit GeneReviews to learn more about how often this condition occurs.
What is Classic galactosemia
Classic galactosemia is an inherited (genetic) condition that prevents the body from breaking down a sugar called galactose.
Your body gets energy from breaking down galactose in milk and other foods. Several enzymes break down galactose into other substances that your body can use or remove.
There are different types of galactosemia:
- Classic galactosemia (galactosemia type I)
- Galactokinase deficiency (galactosemia type II)
- Galactoepimerase deficiency (galactosemia type III)
The type your baby has depends on which enzyme is not working properly to break down galactose.
Classic galactosemia is the most common type of galactosemia and results when an enzyme called GALT, which processes galactose, does not work correctly.
Milder forms of classic galactosemia include:
- Clinical variant galactosemia: People with this form have a small amount of working GALT enzyme, and can process some galactose, but not enough to avoid symptoms.
- Duarte galactosemia: People with this form have enough working GALT enzyme to experience either mild symptoms or no symptoms at all.
When you cannot break down galactose, undigested sugars build up in the body and can cause damage. If untreated, this damage can cause the signs and symptoms of the condition.
Newborn Screening and Follow-Up
Newborn screening for classic galactosemia is done using a small amount of blood collected from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.
During screening, a special machine measures how much of the enzyme GALT is in your baby’s blood. GALT helps break down the milk sugar known as galactose, which your body can then use for energy.
In some cases, the screening will also measure how much total galactose is in your baby’s blood. If the GALT enzyme cannot break down galactose, then there will be higher than normal levels of galactose in the body. Babies with low levels of GALT activity, either with or without high levels of total galactose, might have classic galactosemia.
If your baby’s blood spot screening result for classic galactosemia is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.
An out-of-range screening result does not mean that your baby definitely has the condition. It does mean that your baby needs more follow-up testing. To learn more about screening results, visit the Blood Spot Screening Results page.
Your baby may need the following tests after an out-of-range screening result:
- Blood and/or urine tests
- Genetic testing using a blood sample
You should complete any recommended follow-up testing as soon as possible. Babies with this condition can have serious health problems very soon after birth if they are not diagnosed and treated quickly.
False-positive newborn screening results for this condition can happen.
- Samples exposed to too much heat or took too long to get to the screening laboratory can also have false-positive results.
- Sometimes, babies who have another condition called G6PD can screen positive for classic galactosemia, even though they do not have the condition.
Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need to get treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.
Signs of classic galactosemia often appear within a few days of birth. Drinking milk the body cannot break down can cause symptoms. Babies with Duarte galactosemia typically show few or no signs or symptoms.
Signs of the condition may include the following:
Classic galactosemia is caused by a change in the GALT gene. This gene gives your body instructions for making the GALT enzyme. GALT breaks down galactose into glucose and other substances that your body uses for energy.
Without a working GALT gene, your baby cannot make enough working GALT enzyme. As a result, their body cannot properly break down and get rid of galactose. High levels of galactose and other undigested sugars can damage their body.
Classic galactosemia results in very little to no working GALT enzyme. People with a milder version of the condition called Duarte galactosemia have some working GALT enzyme.
- Classic galactosemia is an autosomal recessive condition. Babies inherit the condition when each parent passes down a nonworking GALT gene to their baby. Only babies with two nonworking GALT genes—one from the mom and one from the dad—have this condition.
- People with one working copy and one nonworking copy of the GALT gene are called carriers.
- Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
- If two parents are carriers of a nonworking copy of the GALT gene, they have a 1 in 4 chance of having a child with classic galactosemia.
- Carriers for classic galactosemia often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with classic galactosemia.
- Parents who already have a child with classic galactosemia still have a 1 in 4 chance of having another child with classic galactosemia. This 1 in 4 chance stays the same for all future children.
- Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it. Visit the National Society of Genetic Counselors to find a genetic counselor and the American College of Medical Genetics and Genomics to find a medical geneticist.
Treatment and Management
It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.
Treatments may include the following:
- Avoidance of foods that contain galactose and lactose
- Avoidance of all dairy products
- Special foods and formulas
- Vitamin supplements (calcium, vitamin K, vitamin D)
Children who receive early and ongoing treatment for classic galactosemia can have healthy growth and development. Some children with classic galactosemia who receive treatment early still show delays in learning, development, speech/language, and motor skills.