Conditions Galactokinase Deficiency

Galactokinase deficiency (GALK) is an inherited condition in which the body is unable to properly digest galactose, a sugar found in all foods that contain milk and some fruits and vegetables. If a baby with GALK eats food containing galactose, undigested sugars build up in the blood. If GALK is left untreated, affected children develop cataracts. However, when the condition is identified though newborn screening and proper treatment is initiated immediately, individuals with GALK generally have no problems with their eyes.

GALK is only one type of a broader condition group called galactosemia. The different types of galactosemia each have different causes and outcomes. You can read about other types of galactosemia on the pages for classic galactosemia and galactoepimerase deficiency.

Condition Type

Other Disorders


Galactokinase deficiency (GALK) occurs in less than 1 out of every 100,000 births.

Also known as

  • GALK
  • GALK deficiency
  • Galactosemia II

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of GALK (see Early Signs below). If your baby has certain signs, your baby’s doctor may suggest starting immediate treatment.

If your baby’s newborn screening result for galactokinase deficiency (GALK) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, a few babies do have the condition so it is very important that you go to your follow-up appointment for a confirmatory test. Because untreated babies with GALK can develop cataracts during early childhood, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.

Follow-up testing will involve a blood test to measure the amount of certain substances your baby’s blood. Children with GALK have low amounts of the galatokinase 1 enzyme in their blood. Your baby’s doctor may also measure the amount of undigested sugars present in a sample of your baby’s urine. Undigested sugars build up in the body when a child has GALK, so measuring the amounts of these sugars and other substances can help doctors determine if your baby has a condition. Genetic testing for GALK may also be necessary to confirm the diagnosis.

About Galactokinase Deficiency

Early Signs

If your baby has galactokinase deficiency (GALK), you may first notice delayed growth.

Children with untreated GALK usually develop vision trouble during early childhood. This is why early screening and identification is so important.


Dietary Treatments

Your baby may need to avoid foods with galactose (a sugar found in milk) to prevent a toxic build-up of undigested sugars in their blood. Many children with galactokinase deficiency (GALK) need to avoid all milk products

Your baby’s doctor can recommend foods and formulas that do not contain galactose. These will likely need to be continued through adulthood.

Certain fruits and vegetables also contain galactose. Your baby may need to avoid these as well. A dietician or nutritionist can help you plan a healthy diet for your child.


Since many children must avoid milk-containing products, your baby may need to take calcium supplements. Your doctor may also prescribe Vitamin C and Vitamin K supplements.

Expected Outcomes

Children who receive early and on-going treatment for galactokinase deficiency (GALK) can reduce the complications of vision trouble.

Without treatment, children with GALK are at risk of developing cataracts (an eye condition that can lead to impaired vision).


When we eat food, enzymes help break it down. We need to break down the carbohydrates and sugars we eat so that they can be used for energy. Many foods, such as milk products and some fruits and vegetables, contain the sugar galactose. Galactose is broken down by several enzymes including galactokinase 1.

If your baby has galactokinase deficiency (GALK), galactokinase 1 is either missing or not working properly. When this enzyme does not work correctly, galactose cannot be broken down. This causes large amounts of undigested sugars to build up, particularly in the lens of the eye. The build-up can damage the eyes and cause them to become cloudy, leading to blurred vision.

GALK is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for GALK, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with GALK is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

Support for Galactokinase Deficiency

Support Services

Support groups can help connect families who have a child or other family member affected with galactokinase deficiency (GALK) with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates:

Accessing Care

Work with your baby’s doctor to determine the next steps for your baby’s care. Your baby’s doctor may help you coordinate care with a dietician, a doctor who specializes in metabolism, or other medical resources in your community. Usually with treatment, children are able to avoid vision trouble. However, if your child is having trouble with their vision, you may need to see a doctor who treats eye problems.

Because galactokinase deficiency (GALK) is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for GALK, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the American College of Medical Genetics and Genomics (ACMG) and the Find a Genetic Counselor tool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.

Families' Experiences

At this time we have not located a family story for this particular condition. If your family is affected by galactokinase deficiency (GALK) and you would like to share your story, please contact us so other families may learn from your experience.

Each family's experience with a condition is unique, but there are some parts of the evaluation and treatment of GALK that are similar to other types of galactosemia. Please see the Families' Experiences section of our Classic Galactosemia page if you would like to read the stories of families dealing with that type of galactosemia.

References & Sources

Visit OMIM to search its online catalog of human genes and disorders

Visit MedlinePlus Genetics for more condition information

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

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