Definition of Deficiency, GALT

Deficiency, GALT: Lack of the enzyme called GALT (galactose-1-phosphate uridyl transferase) which causes the genetic metabolic disease galactosemia, one of the diseases in many newborn screening panels. The disease can be fatal, if undetected. If detected, it can be treated by avoiding galactose in the diet.

Galactosemia is inherited as an autosomal recessive trait. There are two forms of the disease, GALT deficiency (classic galactosemia) and galactose kinase deficiency. Of the two, the GALT deficiency is the most severe. The GALT gene is in chromosome 9p13.

People with galactosemia are unable to metabolize the simple sugar galactose. Galactose makes up half of the sugar called lactose that is found in milk. Lactose is called a disaccharide, di meaning 2, since lactose is made up of two sugars, galactose and glucose, bound together. If an infant with galactosemia is given milk, galactose builds up in the infants system causing damage to the liver, brain, kidneys and eyes. Individuals with galactosemia cannot tolerate any form of milk (human or otherwise) or any other galactose-containing food. Exposure to milk products will result in liver damage, mental retardation, cataract formation, and kidney failure.

Typically, a newborn infant with galactosemia, upon being fed milk, will develop jaundice, vomiting, lethargy, irritability, and convulsions. The liver is enlarged and the blood sugar may be low. Continued feeding of milk products to the infant leads to cirrhosis of the liver, cataract formation in the eye resulting in partial blindness, and mental retardation.

The symptoms of galactosemia include jaundice (yellowish discoloration of the skin and the whites of the eyes), vomiting, poor feeding, poor weight gain, lethargy, irritability, convulsions, and opacities in the lenses of the eyes. The signs detected include hepatomegaly (enlarged liver), hypoglycemia (low blood sugar), aminoaciduria (amino acids are present in the urine), cirrhosis, ascites (fluid collected within the abdomen), cataracts and mental retardation.

The diagnosis is usually based on the demonstration of a lack of activity of the enzyme GALT in erythrocytes (red blood cells). Prenatal diagnosis is also feasible by direct measurement of the enzyme.

Once the disease is recognized, treatment consists of strictly avoiding all milk and milk containing products. The infant can be fed with soy formula, meat-base formula, or Nutramigen (a protein hydrolysate formula) or other lactose-free formula. The condition is life-long and requires abstinence from milk and milk products for life.

Parents need to take care and educate the child to avoid not only milk and milk products, but also those foods that contain dry milk products. For this reason, it is essential to read product labels and be an informed consumer. If diagnosis is made early and milk products are strictly avoided the prognosis is for a relatively normal life. Despite strict avoidance of galactose mild intellectual impairment may still develop.

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