Galactokinase deficiency is a mild type of an inherited (genetic) condition called galactosemia. Galactosemia prevents the body from breaking down a sugar called galactose correctly.

Your body gets energy to work properly from breaking down galactose found in milk and other foods. Several enzymes break down galactose into substances that your body can either use or remove.

The different types of galactosemia are:

• 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.

In galactokinase deficiency, the enzyme that is not working correctly is called GALK. When this enzyme cannot process galactose, undigested sugars build up. These undigested sugars can create cloudy lenses in the eyes (cataracts) and other signs and symptoms of the condition.

Galactokinase deficiency is caused by a change in the GALK gene. This gene gives your body instructions for making the GALK enzyme that breaks down galactose into glucose and other substances that your body uses for energy.

Without a working GALK gene, your baby's body cannot make enough of the GALK 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.

Galactokinase deficiency is a genetic condition. Babies inherit it from their biological (birth) parents.

• Galactokinase deficiency is an autosomal recessive condition. Babies inherit the condition when each parent passes down a nonworking GALK gene to their baby. Only babies with two nonworking GALK genes—one from the mom and one from the dad—have this condition.
  • People with one working copy and one nonworking copy of the GALK 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 GALK gene, they have a 1 in 4 chance of having a child with galactokinase deficiency.
  • Carriers for galactokinase deficiency 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 galactokinase deficiency.
  • Parents who already have a child with galactokinase deficiency still have a 1 in 4 chance of having another child with galactokinase deficiency. 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.

Signs of galactokinase deficiency may appear shortly after birth or later in childhood. Symptoms can be caused by eating foods or milk that the body cannot break down.

Signs of the condition may include the following:

• Delayed growth
• Cloudy eyes (cataracts)

Newborn screening for galactokinase deficiency is done using a small amount of blood collected from your baby’s heel. During screening, a special machine measures how much of a sugar called galactose is in your baby’s blood. Babies with high levels of galactose might have galactokinase deficiency.

What Happens After an Out-of-Range Screening Result?

If your baby’s blood spot screening result for galactokinase deficiency 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.

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 if they are not diagnosed and treated quickly.

False-positive newborn screening results for this condition can happen. Babies with certain ethnic backgrounds (Hmong/Laotian) may have elevated total galactose results, but not have galactokinase deficiency.

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.

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 galactokinase deficiency can have healthy growth and development.