Pku

1 Pages 238 Words

Phenylketonuria (PKU) is a genetic inborn error of
metabolism that is detectable during the first days of
life with appropriate blood testing (newborn
screening). The absence or deficiency of an enzyme
that is responsible for processing the essential amino
acid phenylalanine characterizes PKU. With normal
enzymatic activity, phenylalanine is converted to
another amino acid (tyrosine), which is then utilized
by the body. However, when the phenylalanine
hydroxylase enzyme is absent or deficient,
phenylalanine abnormally accumulates in the blood and
is toxic to brain tissue.
Without treatment, most infants with PKU develop
mental retardation. Those with untreated PKU may also
develop additional neurologic symptoms.

To prevent mental retardation, treatment consists of a
carefully controlled, phe-restricted diet begun during
the first days or weeks of life. Most experts suggest
that a phe-restricted diet should be lifelong. A
carefully maintained diet can prevent mental
retardation as well as neurological, behavioral and
dermatological problems. It is generally believed that
keeping blood phenylalanine levels in the range of
2-6mg/dl is the safest, especially in infancy and
early childhood. Frequent blood monitoring should be
done to achieve this goal.

PKU is inherited as an autosomal recessive trait. In
other words, two people who conceive a child must both
be carriers of the gene in order for there to be a
chance that their infant will have PKU. When both
carriers conceive a child, there is a one in four or
25% chance for each pregnancy that the baby will have
PKU. It is estimated that PKU occurs in one in 15,000
newborns in the United States. The incidence varies in
other parts of the world....