(Type I: Classic), Galactokinase Deficiency (Type II), and Galactose Epimerase Deficiency (Type III)
Galactosemia is a rare genetic disorder that can cause scarring of the liver (cirrhosis) in infants. Galactosemia affects how much galactose, a simple sugar and the primary element in the larger sugar lactose, is produced. Galactosemia causes a deficiency in a liver enzyme responsible for metabolizing galactose in the blood, resulting in elevated levels of galactose.
A small amount of galactose is present in a variety of foods, including all dairy products and some baby formulas. There are several types of galactosemia, caused by genetic mutations, which affect different enzymes involved in the breaking-down of galactose.
Classic galactosemia( Type I) is the most common, and most severe, type. Galactokinase deficieny( Type II) is a less common, milder type of the disorder. Galactose epimerase deficiency ( Type III) causes different patterns, signs, and symptoms than do the other two types.
Why it is Problematic
If infants with Type I galactosemia are not promptly diagnosed and treated with a low-galactose diet, life threatening complications can occur within a few days of birth. Affected infants typically develop feeding difficulties, lethargy, failure to thrive, jaundice, liver damage, and bleeding. Other serious complications can include sepsis and shock.
Individuals with Type I galactosemia are at an increased risk for cataracts, speech difficulties, and intellectual disability. Females are at risk for reproductive problems and ovarian failure.
Type II galactosemia causes fewer medical problems than Type I. Infants affected with Type II often develop cataracts, but there are few long-term complications associated with the disorder.
Type III galactosemia can produce problems that vary from very mild to severe and may also cause cataracts, delayed growth, impaired development, intellectual disability, liver disease, and kidney problems.
Causes and Risk Factors
Galactosemia is group of genetically inherited disorders following an autosomal recessive pattern characterized by mutations in certain genes. In order for the mutation to be expressed or to have symptoms of the disease, an individual must have two copies (homozygous) of the mutation, one copy received from each parent. Parent carriers having only one copy (heterozygous) do not express the mutation and are not typically afflicted by the disease. Carrier parents have a 1 in 4 chance of having a homozygous child with galactosemia. Mutations resulting in galactosemia make take place in:
- The GALT gene, responsible for causing Type I galactosemia.
- The GALK 1 gene, responsible for causing Type II galactosemia.
- The GALE gene, responsible for causing Type III galactosemia.
Galactosemia symptoms usually appear within the first few days of life. Symptoms become obvious after the ingestion of breast milk or formula. These include:
- Jaundice (yellowing of the skin and whites of the eyes)
- Liver enlargement
Other symptoms may include:
- Severe bacterial infection
- Failure to gain weight
If left untreated or unrecognized liver, brain, kidney, and eye damage could occur.
Blood tests can help reach a galactosemia diagnosis. Enzyme levels in red blood cells, white blood cells and liver cells are measured for activity. If no activity is present, it indicates that the individual is affected by the condition. Carriers of the condition have enzyme levels that are about half that of normal.
Urine tests can measure the amount of galactose that is excreted in the urine; afflicted patients have higher quantities of galactose in their urine. False negatives of urine tests may result if the infant is vomiting. Galactose allergy tests are dangerous and therefore not performed to assist in a galactosemia diagnosis.
Treatment and Prevention
Treatment for galactosemia requires elimination of galactose from the diet. This may include stopping breast feeding and beginning a lactose-free and galactose-free diet. This diet should be strictly adhered to and followed for life.
It is recommended that mothers of infants with galactosemia, as well as women known to be carriers of galactosemia, be placed on galactose-free diets during pregnancy. This is expected to mitigate the severity of symptoms present at birth. If treatment is given early enough, any liver damage sustained in the first few days of life can heal. Because of the value of early detection and dietary restrictions, any infant with jaundice should be screened for galactosemia.
Type I galactosemia affects approximately 1 in 30,000-60,000 newborns. Type II and Type III galactosemia are less common. Type II affects fewer than 1 in 100,00 newborns and Type III is very rare.