Accumulation of galactitol has been attributed to many of the negative effects of galactosemia, and high concentrations of galactitol have been found in people with classic galactosemia (GALT deficiency or Galactose-1-phosphate uridylyltransferase deficiency), galactokinase deficiency, and epimerase deficiency with glucose. Oxidation to galactonate
Accumulated galactose can also undergo an alternative reaction: Oxidation to galactonate. The mechanism of galactonate formation is still unclear. However, recent studies suggest that galactose dehydrogenase is responsible for converting galactose to galactonolactone, which then spontaneously or enzymatically converts to galactonate. Once formed, galactonate may enter the pentose phosphate pathway. Thus, Oxidation to galactonate serves as an alternate pathway for metabolizing galactose. This oxidative pathway renders accumulated galactonate less harmful than accumulated galactitol. Diagnosis
In many states throughout the world, infants routinely undergo newborn screening (NBS) for galactosemia. This allows a diagnosis to be made while the person is still an infant. Infants affected by galactosemia typically present with symptoms of lethargy, vomiting, diarrhea, failure to thrive, and jaundice. None of these symptoms are specific to galactosemia, often leading to diagnostic delays. If the family of the baby has a history of galactosemia, doctors can test prior to birth by taking a sample of fluid from around the fetus (amniocentesis) or from the placenta (chorionic villus sampling or CVS). Galactosemia is normally first detected through newborn screening which if available, is able to diagnose the majority of affected infants.
A galactosemia test is a blood test (from the heel of the infant) or urine test that checks for three enzymes that are needed to change galactose sugar that is found in milk and milk products into glucose, a sugar that the human body uses for energy. A person with galactosemia doesnt have one of these enzymes. This causes high levels of galactose in the blood or urine.Affected children can have serious, irreversible effects or even die within days from birth. It is important that newborns be screened for metabolic disorders without delay. Galactosemia can even be detected through NBS before any ingestion of galactose-containing formula or breast milk. Detection of the disorder through NBS does not depend on protein or lactose ingestion, and, therefore, it should be identified on the first specimen unless the infant has been transfused. A specimen should be taken prior to transfusion. The enzyme is prone to damage if analysis of the sample is delayed or exposed to high temperatures. The routine NBS is accurate for detection of galactosemia. Two screening tests are used to screen infants affected with galactosemia—the Beutlers test and the Hill test. The Beutlers test screens for galactosemia by detecting the level of enzyme of the infant. Therefore,  the ingestion of formula or breast milk does not affect the outcome of this part of the NBS, and the NBS is accurate for detecting galactosemia prior to any ingestion of galactose.