Galactosemias

Newborn Screening for Galactosemia

What Is Galactosemia?

Classic Galt • Galk • Gale • Duarte

Galactosemia is a family of genetic disorders that result from compromised ability to metabolize the sugar galactose; the term "galactosemia" literally means too much galactose in the blood. Galactose is found in milk and all foods that contain milk. Infants with galactosemia usually have diarrhea and vomiting within a few days of drinking milk or formula containing lactose.

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 galactosemia, neither of these genes works correctly. These children inherit one non-working gene for the condition from each parent.

Parents of children with galactosemia rarely have the condition themselves. Instead, each parent has a single non-working gene for galactosemia. They are called carriers. Carriers do not have galactosemia because the other gene of this pair is working correctly.

When both parents are carriers, there is a 25% chance in each pregnancy for the child to have 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.

Galactosemia is a condition with multiple forms, each of which have different causes and outcomes. The types of galactosemia include the following:

Classic Galactosemia (GALT, Type 1)

Classic galactosemia is a rare, serious, life-threatening disorder and occurs in one in every 30,000 to 60,000 newborns. GALT occurs in people of all ethnic groups, but it is most common in people of Irish descent. GALT is an inherited condition in which the body is unable to properly digest galactose, a sugar found in all foods that contain milk. If a child with GALT eats galactose, undigested sugars build up in the blood rather than being used for energy. Signs of GALT can appear within a few days after birth.

Early signs of GALT include:

  • Poor weight gain and growth
  • Poor feeding and sucking
  • Vomiting
  • Diarrhea
  • Sleeping longer or more often
  • Tiredness
  • Irritability
  • Low blood sugar (hypoglycemia)

Some of the other early effects of untreated galactosemia include:

  • Failure to gain weight or grow in length
  • Poor feeding and poor suck
  • Lethargy
  • Irritability

If treatment is not started, other symptoms are likely to follow:

  • Low blood sugar, called hypoglycemia
  • Seizures
  • Enlarged liver that does not work properly
  • Jaundice
  • Bleeding
  • Serious blood infections that could lead to shock and death
  • Early cataracts which occur in about 10% of children
  • Some untreated babies have high levels of ammonia, a toxic substance, in their blood. High ammonia levels and hypoglycemia can both lead to coma and, if not treated, can cause death.
  • Most untreated children eventually die of liver failure
  • Surviving babies who remain untreated may have intellectual disabilities and other damage to the brain and nervous system

Even with adequate treatment, individuals with galactosemia may develop one or more of the following:

  • Early cataracts
  • Mild intellectual disabilities or learning delays
  • Ataxia (unsteady gait)
  • Delays in growth
  • Speech problems and delays
  • Most girls with galactosemia will have delayed periods or do not get their periods at all

Galactokinase Deficiency (GALK, Type 2)

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.

If your baby has GALK, you may first notice delayed growth. Children with untreated GALK usually develop vision trouble during early childhood.

Galactoepimerase Deficiency (GALE, Type 3)

GALE is an inherited condition in which the body is unable to properly break down galactose, a sugar found in all foods that contain milk and in some fruits and vegetables. This condition can cause harmful amounts of undigested sugars to build up in the blood. There are three forms of GALE (generalized, peripheral, and intermediate). Some of these forms are more severe, while others are milder. Severe forms of GALE can lead to eye problems (cataracts), delayed growth and development, intellectual disabilities, liver disease, kidney problems or even death.

There are three forms of GALE, which vary by the severity of their signs: generalized, peripheral, and intermediate. Signs of generalized GALE usually start shortly after birth and include:

  • Weak muscle tone (hypotonia)
  • Poor feeding and sucking
  • Vomiting
  • Weight loss

Babies with peripheral or intermediate GALE generally do not develop any signs of the condition.

Duarte Galactosemia (DG)

DG, while more common, is far less severe. Many individuals with DG never develop any symptoms due to this condition. DG 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. The decision of whether or not to treat someone with DG depends in part on the level of galactose in the blood.

The following are treatments often advised for children with classic galactosemia:

  1. Lactose and galactose-free diet
    People with classic galactosemia are encouraged to follow a lactose and galactose-free food plan throughout life.
  2. Special lactose-free formula
    The most common formulas used for babies with galactosemia are those made with soy protein isolate. Soymilk contains galactose and should not be used.
  3. Calcium supplements
    Since children with galactosemia are not eating milk products, calcium intake may be too low. Therefore, children with galactosemia are often advised to take calcium supplements to ensure they receive enough calcium each day.
    Some doctors also advise Vitamin D and Vitamin K supplements in addition to calcium.
  4. Monitoring health
    Babies and young children with galactosemia usually need regular blood and urine tests. These tests are used to detect toxic substances made when galactosemia is not in good control. The test results will help your doctors and dietitian fine-tune the treatment to meet your child's needs.
    Your doctor may also suggest a formal evaluation of your child's mental development and his or her speech and language skills. If your child shows delays in certain areas of learning or speech, extra help can be arranged. Early intervention programs are available in most states to provide services before children reach school age.
  5. Informing friend, relatives, teachers and child-care providers
    It is important for you to tell everyone who helps care for your child that he or she cannot eat or drink milk-containing foods. A Medic-Alert bracelet that states your child's food restrictions can be helpful. In addition, your doctor may advise you to carry an emergency treatment letter with steps for your child's care.

References:

  • newbornscreening.info
  • babysfirstest.org
  • marchofdimes.org