Galactosemia is a rare genetic metabolic disorder that impairs the body’s ability to process galactose, a sugar in milk and dairy products. It results from a deficiency in enzymes that break down galactose into glucose, the body’s primary energy source. When these enzymes are diminished or missing, galactose or its byproducts accumulate to toxic levels in the blood and tissues. Early detection through testing is important to manage this condition effectively.
Why Galactosemia Testing is Crucial
If galactosemia is not identified and managed promptly, health consequences can arise shortly after birth. Infants with classic galactosemia, the most common and severe form, may develop feeding difficulties, lethargy, jaundice, and an enlarged liver within days of consuming milk. Toxic substance accumulation can lead to liver damage, kidney failure, and life-threatening bacterial infections like E. coli sepsis. Without intervention, these complications can be fatal.
Beyond the immediate dangers, untreated galactosemia can result in long-term neurological impairments and developmental issues. Children may experience intellectual disabilities, speech difficulties, and problems with fine and gross motor skills. Cataracts, a clouding of the eye lens, are also a common complication due to the buildup of galactitol in the eye. Females with classic galactosemia often develop premature ovarian insufficiency, leading to reproductive problems. Early diagnosis through newborn screening allows for immediate dietary intervention, which can prevent or significantly reduce these severe outcomes.
How Galactosemia is Tested
Galactosemia testing begins with routine newborn screening, a standard procedure performed shortly after birth. This involves a heel prick to collect a few drops of blood, placed on a filter paper (Guthrie card). This initial screen checks for several metabolic disorders, including galactosemia, by measuring levels of galactose and related substances in the blood. While effective in detecting classic galactosemia, this is a preliminary screening.
If the newborn screen yields a positive or suggestive result, further diagnostic tests are necessary to confirm the diagnosis. These confirmatory tests involve additional blood samples. Clinicians may perform enzyme assays to measure the activity of the galactose-1-phosphate uridyltransferase (GALT) enzyme, which is deficient in classic galactosemia. Elevated levels of galactose-1-phosphate in red blood cells also indicate the condition. Genetic testing may also identify specific mutations in the GALT gene.
If there is a known family history of galactosemia, prenatal testing can be considered. Procedures like amniocentesis or chorionic villus sampling can analyze fetal cells for the genetic mutations associated with the disorder. These tests are performed during pregnancy to provide an early indication of the condition, though the primary focus remains on infant testing after birth.
Understanding Test Results and Next Steps
A negative newborn screening result indicates that galactosemia is unlikely. However, if the newborn screen is positive or suggestive, it does not automatically confirm a diagnosis of galactosemia. Instead, it signals the need for urgent confirmatory testing. While awaiting definitive results, mothers are advised to temporarily stop breastfeeding and switch to a soy-based or dairy-free formula to minimize galactose exposure.
Upon a confirmed diagnosis of galactosemia, immediate action is taken to prevent complications. The primary intervention involves strict elimination of lactose and galactose from the infant’s diet. This means avoiding breast milk, standard cow’s milk-based formulas, and any dairy products. Infants are fed specialized formulas, such as soy-based or elemental formulas, that are free of galactose.
Parents will work closely with a team of specialists, including metabolic geneticists and registered dietitians, to manage the condition. Regular follow-up appointments are scheduled to monitor the child’s health and development. Even with a strict diet, some individuals may still experience long-term complications, requiring ongoing management and monitoring.