Galactosemia
Alternative names
Galactose-1-phosphate uridyl
transferase deficiency; Galactokinase deficiency;
Galactose-6-phosphate epimerase deficiency
Definition
Galactosemia is the inability
of the body to use (metabolize) the simple sugar
galactose (causing the accumulation of galactose
1-phosphate), which then reaches high levels in
the body, causing damage to the liver, central
nervous system, and various other body systems.
Causes
and risks
Galactosemia is an inherited disorder (transmitted
as an autosomal recessive trait). It occurs
at a rate of approximately 1 out of 60,000 births.
There are 3 forms of the disease -- galactose-1
phosphate uridyl transferase deficiency (classic
galactosemia) and deficiency of galactose kinase
or galactose-6-phosphate epimerase. Of
these, the galactose-1-phosphate transferase
deficiency is the most severe (and more common).
People with galactosemia are unable to fully metabolise
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 and saccharide meaning sugar) since
lactose is made up of two sugars, galactose
and glucose, bound together.
If an infant with galactosemia is given milk,
derivatives of 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 animal),
or must carefully watch intake of other
galactose-containing foods. Exposure to milk
products may result in liver damage, mental
retardation, cataract formation, and kidney
failure.
After drinking milk for a few days, a newborn
infant with galactosemia, will develop intolerance
of feeding, 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
(which may result in partial blindness), and
mental retardation.
Prevention
A personal knowledge of family history is helpful.
If there is a family history of galactosemia,
genetic counseling will help prospective
parents make decisions about pregnancy and
prenatal testing. Once the diagnosis of galactosemia
is made, genetic counseling is recommended for
other members of the family.
Many states have mandatory screening for galactosemia
in newborn's blood. Parents may receive
a call from a health care provider that says
the screening test indicates possible galactosemia. At
that time, the parents should promptly stop
milk products and have a blood test done for
galactosemia through their doctor.
Symptoms
- Jaundice (yellowish discoloration of the
skin and the whites of the eyes)
- Vomiting
- Poor feeding (baby refusing to drink
milk-containing formula)
- Poor weight gain
- Lethargy
- Irritability
- Convulsions
Signs
and tests
- Hepatomegaly (enlarged liver)
- Hypoglycemia (low blood sugar)
- Aminoaciduria (amino acids are present in
the urine)
- Cirrhosis
- Ascites (fluid collects in the abdomen)
- Mental retardation
- Cataract formation
Tests include:
- Prenatal diagnosis by direct measurement
of the enzyme galactose-1-phosphate uridyl
transferase.
- Reducing substances in infants urine with
simultaneous normal or low blood sugar while
the infant is being fed breast milk or a formula
containing lactose. One simple test on the
urine with Clinitest indicates the presence
of a reducing substance, and a specific enzymatic
study on the urine can prove the substance
to be galactose.
- Presence of chemical, called ketones, in
urine.
- Measurement of enzyme activity in erythrocytes
(red blood cells).
- Blood culture for bacteria infection (E.
coli sepsis).
Treatment
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 lifelong 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.
Prognosis
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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