Galactosemia
An inherited inability to break down the milk sugar galactose
Quick Facts
- Type: Inherited metabolic disorder
- Problem sugar: Galactose (from lactose in milk)
- Detection: Newborn screening
- Main treatment: Lifelong galactose-restricted diet
Overview
Galactosemia is a rare inherited disorder that affects how the body processes galactose, a simple sugar that is part of lactose, the main sugar in milk. People with galactosemia are missing or short of an enzyme needed to break galactose down. As a result, galactose and related substances build up in the body and can damage organs such as the liver, brain, kidneys, and eyes.
The most common and serious form is classic galactosemia, caused by a deficiency of the enzyme GALT. Symptoms usually appear within the first days of life once a baby begins feeding on breast milk or standard formula. Because early treatment is essential, galactosemia is included in routine newborn screening in many places, allowing the diet to be changed before serious harm occurs.
Symptoms
In classic galactosemia, symptoms typically begin in the first days to weeks of life after milk feeding starts:
- Poor feeding and vomiting
- Jaundice, yellowing of the skin and eyes
- Poor weight gain and failure to thrive
- An enlarged liver and signs of liver problems
- Lethargy, irritability, and in severe cases a serious bloodstream infection (sepsis)
If untreated, galactosemia can be life-threatening in infancy and can lead to lasting problems such as cataracts, learning difficulties, and, in girls, effects on ovarian function later in life. Prompt dietary treatment greatly reduces these risks.
Causes
Galactosemia is caused by inherited changes in the genes that provide instructions for enzymes that break down galactose. In classic galactosemia, the affected gene is GALT.
- Enzyme deficiency: without enough working enzyme, galactose and a related toxic substance accumulate in the blood and tissues.
- Inheritance: the disorder is autosomal recessive, so a child must inherit an altered copy of the gene from each parent.
There are also milder variant forms caused by changes in other enzymes in the galactose pathway, which can range from harmless to significant depending on the type.
Risk Factors
- Two parents who each carry a galactosemia gene change
- A family history of galactosemia
- Parents who are blood relatives
- A previously affected child in the family
Diagnosis
Galactosemia is most often detected before symptoms become severe through routine newborn screening.
- Newborn screening: a heel-prick blood test checks for signs of the enzyme deficiency in many regions.
- Enzyme testing: blood tests measure the activity of the GALT enzyme to confirm the diagnosis.
- Blood and urine tests: may show elevated galactose-related substances.
- Genetic testing: identifies the specific gene changes and the type of galactosemia.
A positive screening result is followed by confirmatory testing, and treatment is started promptly while results are confirmed.
Treatment
The cornerstone of treatment is removing galactose from the diet as completely as possible, for life.
- Galactose-restricted diet: avoiding breast milk, standard infant formula, and dairy products; affected babies are fed soy-based or other special formulas.
- Lifelong dietary management: continuing to limit milk, dairy, and other galactose-containing foods, with guidance from a dietitian.
- Monitoring and support: regular check-ups to watch growth, development, vision, and, in girls and women, ovarian function.
- Supportive care: treating complications such as cataracts or developmental needs as they arise.
Even with excellent diet control, some long-term effects can occur, so ongoing specialist follow-up is important. Early treatment, however, prevents the most serious harm in infancy.
Prevention
Galactosemia cannot be prevented because it is inherited, but its most dangerous effects can be avoided with early detection and strict diet:
- Newborn screening to identify affected babies before symptoms become severe
- Immediate removal of galactose from the diet once diagnosed
- Lifelong adherence to a galactose-restricted diet
- Genetic counseling for families with a known history or carrier status
When to See a Doctor
If newborn screening flags galactosemia, follow up urgently for confirmatory testing and to start the special diet right away. Seek emergency care if a newborn or infant has:
- Repeated vomiting and refusal to feed
- Worsening jaundice, lethargy, or difficulty waking
- Poor weight gain or signs of dehydration
- Fever or signs of serious infection
Untreated galactosemia can become life-threatening quickly in infancy, so prompt medical attention is essential.
Frequently Asked Questions
What causes galactosemia?
Galactosemia is caused by an inherited deficiency of an enzyme that breaks down galactose, a sugar in milk. In classic galactosemia the missing enzyme is GALT, and the condition is passed on when a child inherits an altered gene copy from each parent.
How is galactosemia treated?
The main treatment is a strict, lifelong diet that avoids galactose, found in breast milk, standard formula, and dairy products. Affected infants are switched to soy-based or other special formulas, and ongoing care from a dietitian and specialists is important.
Can a baby with galactosemia breastfeed?
No. Breast milk contains lactose, which the body breaks into galactose, so babies with classic galactosemia cannot breastfeed and need a galactose-free formula instead. This is one reason early diagnosis is so important.
Is galactosemia detected at birth?
In many places it is found through routine newborn screening, which allows treatment to begin before serious harm occurs. A positive screen is confirmed with enzyme and genetic testing while the special diet is started promptly.
Can galactosemia cause lasting problems even with treatment?
Yes. Strict diet prevents the most serious harm in infancy, but some long-term effects, such as learning difficulties or, in girls, effects on ovarian function, can still occur. This is why lifelong monitoring and specialist follow-up are recommended.
References
- MedlinePlus, U.S. National Library of Medicine. Galactosemia.
- Genetic and Rare Diseases Information Center (GARD). Galactosemia.
- National Institutes of Health (NIH). Newborn screening.
- National Organization for Rare Disorders (NORD).