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Galactosemia (British galactosaemia, from Greek γαλακτόζη + αίμα, meaning galactose + blood, accumulation of galactose in blood) is a rare genetics Metabolism Disease that affects an individual's ability to metabolize the sugar galactose properly. Galactosemia follows an autosomal recessive mode of inheritance that confers a deficiency in an enzyme responsible for adequate galactose degradation.
Friedrich Goppert (1870–1927), a German physician, first described the disease in 1917, with its cause as a defect in galactose metabolism being identified by a group led by Herman Kalckar in 1956. Galactosemia was the second disorder found to be detectable through newborn screening methods by Robert Guthrie.
Its incidence is about 1 per 60,000 births for people of European ancestry. In other populations the incidence rate differs. Galactosemia is about one hundred times more common (1:480 births) in the Irish Traveller population.
Progression of this acute neonatal toxicity syndrome may include the development of sepsis, cataracts, and even pseudotumor cerebri (which may cause a bulging of fontanelle).
Image:Lactose Haworth.svg|[[Lactose]]
File:Beta-D-Glucopyranose.svg|[[Glucose]]
File:Beta-D-Galactopyranose.svg|[[Galactose]]
Lactose in food (such as dairy products) is broken down by the enzyme lactase into glucose and galactose. In individuals with galactosemia, the enzymes needed for further metabolism of galactose (Galactokinase and galactose-1-phosphate uridyltransferase) are severely diminished or missing entirely, leading to toxic levels of galactose or galactose 1-phosphate (depending on which enzyme is missing) in various tissues as in the case of classic galactosemia, resulting in hepatomegaly (an enlarged liver), cirrhosis, kidney failure, , vomiting, seizure, hypoglycemia, lethargy, brain damage, and ovarian failure. Without treatment, mortality in infants with galactosemia is about 75%.
Galactosemia is inherited in an autosomal recessive manner, meaning a child must inherit one defective gene from each parent to show the disease. Heterozygotes are carriers, because they inherit one normal gene and one defective gene. Galactosemia The University of Utah, Genetics Science Learning Center. 2008. Carriers show no symptoms of galactosemia.
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 does not have one of these enzymes. This causes high levels of galactose in the blood or urine.
Galactosemia can 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 Beutler's test and the Hill test. The Beutler's 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.
Duarte galactosemia is a milder form of classical galactosemia and usually has no long term side effects. Duarte galactosemia (DG or D/G galactosemia) , Minnesota Department of Health
| classic galactosemia | |
| galactokinase deficiency | |
| galactose epimerase deficiency, UDP-Galactose-4-epimerase deficiency | |
Lactose-restricted diet is efficient in resolving acute complications; however, it is not sufficient to prevent long-term complications affecting the brain and female gonads. Some individuals may experience long-term complications such as speech difficulties, learning disabilities, neurological impairment (e.g. tremors, etc.), and ovarian failure.
Symptoms that have not been associated with Duarte galactosemia, and many individuals with Duarte galactosemia, do not need to restrict their diet at all. However, research corroborates a previously overlooked theory that Duarte galactosemia may lead to language developmental issues in children with no clinical symptoms. Infants with classic galactosemia cannot be breast-fed due to lactose in human breast milk which consists of both galactose and glucose and are usually fed a soy-based formula.
Galactosemia is sometimes confused with lactose intolerance, but galactosemia is a more serious condition. Lactose intolerant individuals have an acquired or inherited shortage of the enzyme lactase, and experience abdominal pains after ingesting dairy products, but no long-term effects. In contrast, a galactosemic individual who consumes galactose can have serious complications including:
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