Definition of Galactosemia
Galactosemia definition - medical term A genetic metabolic disease in which there is a defect in
the body's ability to use the sugar galactose. In classic galactosemia, the basic
defect is a deficiency of the enzyme known as GALT (galactose-1-phosphate uridyl
transferase). This causes an accumulation of galactose 1-phosphate which damages
the liver, eye, brain and kidney. Galactosemia is 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 galactosemis 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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