Galactose Intolerance: Causes, Symptoms and Treatment
Galactose intolerance refers to the body's inability to properly metabolize galactose. It can cause serious health complications and requires a strict low-galactose diet.
Things worth knowing about "Galactose Intolerance"
Galactose intolerance refers to the body's inability to properly metabolize galactose. It can cause serious health complications and requires a strict low-galactose diet.
What is Galactose Intolerance?
Galactose intolerance is an umbrella term for metabolic disorders in which the body is unable to break down the simple sugar galactose properly. Galactose is a naturally occurring sugar found mainly in milk and dairy products – bound together with glucose as lactose – but also in small amounts in some vegetables and legumes. When galactose cannot be fully processed, it accumulates in the blood and organs, causing serious damage over time.
In clinical practice, several distinct forms of galactosemia are recognized, all falling under the spectrum of galactose intolerance. The most common and most severe form is classic galactosemia, caused by a deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT).
Causes
Galactose intolerance is almost always genetic in origin. It follows an autosomal recessive inheritance pattern, meaning a child must inherit one defective gene copy from each parent in order to develop the condition.
- Classic galactosemia (Type I): Deficiency of the GALT enzyme; the most common and most severe form
- Galactosemia Type II (galactokinase deficiency): Deficiency of the galactokinase enzyme; primarily causes cataracts
- Galactosemia Type III (galactose epimerase deficiency): A rarer form with variable severity
In all forms, galactose or its metabolites (especially galactose-1-phosphate and galactitol) accumulate in organs such as the liver, kidneys, brain, and eyes, causing progressive damage.
Symptoms
Symptoms vary depending on the type and severity of the condition. In classic galactosemia, the first signs typically appear shortly after birth, when the newborn begins feeding on breast milk or standard infant formula.
- Vomiting and diarrhea
- Jaundice (yellowing of the skin and eyes)
- Liver enlargement and liver damage
- Poor weight gain and failure to thrive
- Cataracts (clouding of the eye lens)
- Sepsis (bloodstream infection), often caused by E. coli bacteria
- Intellectual and developmental delays if left untreated
- Long-term: cognitive difficulties, speech problems, and primary ovarian insufficiency in women
Diagnosis
Diagnosis is most commonly made through newborn screening, which is performed routinely shortly after birth in many countries including Germany and the United States. Blood samples are analyzed for elevated galactose levels and enzyme activity.
- Blood test (newborn screening): Measurement of galactose and galactose-1-phosphate in the blood
- Enzyme activity assay: Detection of GALT, galactokinase, or epimerase deficiency in red blood cells
- Molecular genetic testing: Confirmation of the diagnosis by identifying the specific gene mutations involved
- Urine analysis: Detection of galactose and galactitol in the urine
Treatment
The only effective treatment for galactose intolerance is a lifelong low-galactose diet. There is currently no enzyme replacement therapy or medication that can substitute for the missing enzyme activity.
Dietary Therapy
- Complete elimination of milk and dairy products (the primary source of galactose)
- Avoidance of galactose-containing foods such as certain legumes and organ meats
- Use of specialized galactose-free infant formulas (e.g., soy-based or amino acid-based formulas)
- Calcium supplementation to compensate for the elimination of dairy products
Long-Term Management
Even with a strict diet, long-term complications can occur, including learning difficulties, speech and language problems, and premature ovarian insufficiency in females. Regular medical follow-up and ongoing care at specialized metabolic centers are therefore essential.
References
- Bosch AM. - Classical galactosaemia revisited. - Journal of Inherited Metabolic Disease, 2006. DOI: 10.1007/s10545-005-0232-0
- Orphanet - Galactosemia disease entry - www.orpha.net (accessed 2024)
- Waisbren SE et al. - Outcome at 4 years of age in a prospective study of children with galactosaemia. - JIMD Reports, 2012. DOI: 10.1007/8904_2011_94
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