Galactosemia is a disorder that affects how
the body processes a simple sugar called galactose.
A small amount of galactose is present in many foods.
It is primarily part of a larger sugar called lactose,
which is found in all dairy products and many baby formulas.
The signs and symptoms of galactosemia result from an
inability to use galactose to produce energy.
Researchers have identified several types of galactosemia.
These conditions are each caused by mutations in a particular
gene, and affect different enzymes involved in breaking
down galactose. Classic galactosemia, also known as
type I, is the most common and most severe form of the
condition. Galactosemia type II (also called galactokinase
deficiency) and type III (also called galactose epimerase
deficiency) cause different patterns of signs and symptoms.
If infants with classic galactosemia are not treated
promptly with a low-galactose diet, life-threatening
complications appear within a few days after birth.
Affected infants typically develop feeding difficulties,
a lack of energy (lethargy), a failure to gain weight
and grow as expected (failure to thrive), yellowing
of the skin and whites of the eyes (jaundice), liver
damage, and bleeding. Other serious complications of
this condition can include overwhelming bacterial infections
(sepsis) and shock. Affected children are also at increased
risk of delayed development, clouding of the lens of
the eye (cataract), speech difficulties, and mental
retardation. Females with classic galactosemia may experience
reproductive problems caused by ovarian failure.
Galactosemia type II causes fewer medical problems than
the classic type. Affected infants develop cataracts,
but otherwise experience few long-term complications.
The signs and symptoms of galactosemia type III vary
from mild to severe and can include cataracts, delayed
growth and development, mental retardation, liver disease,
and kidney problems.
Classic galactosemia occurs in 1 in 30,000 to 60,000
newborns. Galactosemia type II and type III are less
common; type II probably affects fewer than 1 in 100,000
newborns and type