Does this test have other names?
Classic galactosemia; galactosemia type I; galactokinase deficiency disease; galactosemia type II; galactose epimerase deficiency; galactosemia type III; galactose-1-phosphate uridyl-transferase deficiency disease; UDP-galactose-4-epimerase deficiency disease; UDP glucose 4-epimerase deficiency disease; UDP glucose hexose-1-phosphate uridylyltransferase deficiency; UTP hexose-1-phosphate uridylyltransferase deficiency; Duarte galactosemia
What is this test?
This test looks for enzyme activity in the red blood cells in your child's blood.
Galactosemia is a rare inherited disorder that prevents the body from breaking down a simple sugar called galactose. Galactose is found in lactose, which is the sugar in dairy products. Normally, when you eat something that contains lactose, your body breaks lactose down into galactose and glucose. A child who inherits the genes that prevent the breakdown of galactose ends up with too much of it in his or her blood. This condition is called galactosemia. Galactosemia can cause serious problems, such as an enlarged liver, kidney failure, and brain damage.
Out of many types of galactosemia, doctors have identified three main ones. A mutation in a gene determines the type of galactosemia.
Mutations in the GALT gene are responsible for classic type I. This mutation eliminates normal processing of galactose and can be life-threatening within a few days after birth. These newborns may fail to thrive, refuse feeding, and develop jaundice and possibly liver damage. Longer-term problems include cataracts, an increased risk of delayed development, speech difficulties, and reproductive problems from ovarian failure. Type I requires a mutated GALT gene from both parents. If only one parent has a mutated GALT gene and the other has a Duarte variant, then the child will be able to process some galactose. Symptoms of Duarte galactosemia are much less severe.
Mutations in the GALK1 gene create type II galactosemia. Infants with this type of galactosemia can develop cataracts but usually don't have long-term complications.
Mutations in the GALE gene create type III galactosemia. This last type is quite rare. The symptoms vary from mild to severe. Cataracts, intellectual disability, kidney problems, liver disease, and delayed growth are all possible with type III galactosemia.
Why does my child need this test?
This test is part of routine newborn screening. If the routine test comes back positive, you will no longer be able to breastfeed your child. Your child can have soy or another nondairy formula. Further tests will be ordered to determine which type of galactosemia your child has.
Your child might also have this test if he or she has galactosemia and the doctor is watching the deficiency. This is the recommended test schedule:
Every three months until age 1
Every four months until age 2
Every six months until age 14
Girls may need more frequent follow-up to watch for ovarian failure so that appropriate treatment can be given. Both boys and girls are monitored for growth delay, cataracts, and neurodevelopmental impairment.
Children older than 14 and adults with this condition should be tested each year.
What other tests might my child have along with this test?
Your child's doctor may also order a test for GALT deficiency if your newborn is vomiting, is resisting feeding, is jaundiced, has diarrhea, is lethargic, or shows signs of sepsis or enlarged liver.
Your child's doctor may also order a test for GALK deficiency if your newborn seems to be developing a cataract, or something that looks like a dust cloud on the eye lenses.
What do my child's test results mean?
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Normal results show enzyme activity in your child's red blood cells.
Results that show less or no enzyme activity mean that your child may have galactosemia.
Your child's doctor will order other tests to find out which type of deficiency your child has. A GALE deficiency can be found by looking at the total galactose measure on the newborn screen results.
How is this test done?
This test requires a blood sample, which is usually taken by a heel prick in the first week of life.
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection, or bruising.
What might affect my child's test results?
Having breast milk will affect your child's results, as will having a blood transfusion.
How do I get my child ready for this test?
Your child doesn't need to prepare for this test.
- Fraser, Marianne, MSN, RN
- Sohrabi, Farrokh, MD