Galactosemia Symptoms & Causes

The Metabolism Program, located within the Division of Genetics at Boston Children’s Hospital, has extensive experience evaluating and treating infants with galactosemia. Our dedicated team of physicians will work with you every step of the way to provide the life-long care your child needs.

We’ve provided answers to many commonly asked questions about galactosemia in the following pages. When you meet with our team of doctors, they’ll be able to explain your child’s condition and treatment options fully.

What is galactosemia?

Galactosemia means “galactose in the blood”. Babies with this metabolic condition are not able to metabolize a certain type of sugar (galactose) found primarily in breast milk, cow’s milk, and dairy products.  When galactose can’t be broken down and digested, it builds up in the tissues and blood in large amounts. Its byproducts also build up in large amounts.

Because they are poisonous for the body, galactosemia may be life-threatening if not treated right away.

Are there different types of galactosemia?

Three types of galactosemia have been identified. They are caused by a mutation in the GALE, GALK1, and GALT genes. These three genes are responsible for making all of the enzymes that are essential for breaking down (metabolizing) galactose.  Almost all of the patients with galactosemia have the classic or life-threatening form of the disease due to severe GALT deficiency.

For the purposes of this webpage, the information below will only focus on classic galactosemia, the most common type of galactosemia that result from mutations in the GALT gene.

  • The variant Duarte galactosemia, a much milder form of galactosemia, also involves a mutation in the GALT gene. Whereas classic galactosemia completely prevents the normal processing of galactose, the Duarte variant only reduces enzyme activity by ~75%, but not by 100% as in classic galactosemia. Children with Duarte galactosemia usually do not have serious health effects and may or may not need treatment.

Other types of classic galactosemia, far rarer, that are not discussed here include:

  • Galactosemia type II, caused by results from mutations in the GALK1 gene
  • Galactosemia type III, caused by mutations in the GALE gene


What causes galactosemia?

Classic galactosemia occurs when an enzyme called galactose-1-phosphate uridyltransferase (GALT) is missing or not functional. This liver enzyme is responsible for breaking down galactose (a sugar byproduct of lactose found in breast milk, cow’s milk and other dairy foods) into glucose. When galactose cannot be changed to glucose, it, as well as its byproducts such as galactose-1-phosphate, builds up in tissues and blood and affects many parts of the body.

This hereditary condition is passed from parent to child as an autosomal recessive disease. This means that a child needs to inherit two copies of the defective gene (one from each parent) in order to have the disease. 

Signs and symptoms

What are the initial signs of galactosemia?

A baby may develop signs of galactosemia within the first few days of life if the consume lactose found in breast milk or baby formula.

These initial signs include:

  • Refusal to eat
  • Spitting up or vomiting
  • Yellowing of the skin (jaundice) Lethargy
  • Cataracts

Do any signs and symptoms show up later on in life?

Even if children receive treatment at an early age, delays in learning and development, as well as speech defects, are common. The specific issues and level of delay varies from child to child, but may include:

  • Learning disabilities
  • Delay in language acquisition
  • Problems with speech are common(majority of children with classic galactosemia have speech disorders)
  • Difficulty with fine and gross motor skills
  • Difficulty with math and reading
  • Neurological impairments
  • Problems with gait, balance, fine motor tremors affecting (affecting a minority of children and adults).
  • Inability to coordinate voluntary movements (ataxia)
  • Involuntary muscle contractions (tremors)
  • Inaccurate estimation of distance during muscular activity (dysmetria).
  • Ovarian failure
  • Almost all females with severe or classic galactosemia develop premature ovarian insufficiency (POI, a condition in which the ovaries stop releasing eggs earlier than normal).
  • Although the exact cause is not known, it is believed that galactose or its byproduct may be toxic to the ovaries. Most females are unable to have children as a result of this premature loss of ovarian function, which resembles early menopause.