Download Phenylketonuria

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By: Christine Emerald G. Rivera
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* Phenylketonuria: The inherited inability to
metabolize (process) the essential amino acid
phenylalanine due to complete or near-complete
deficiency of the enzyme phenylalanine
hydroxylase.
Newborns are screened for phenylketonuria (PKU)
by a blood test, usually with the Guthrie card
bloodspot obtained from a heelprick.
Phenylketonuria is inherited in an autosomal
recessive manner, as are lesser degrees of
phenylalanine hydroxylase deficiency.
Phenylketonuria is abbreviated and commonly
referred to as PKU.
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Phenylketonuria is a genetic disorder inherited
from a person's parents. It is due to mutations in
the PAH gene which results in low levels of the
enzyme phenylalanine hydroxylase. This results
in the build up of dietary phenylalanine to
potentially toxic levels. It is autosomal recessive
meaning that both copies of the gene must be
mutated for the condition to develop. There are
two main types, classic PKU and variant PKU,
depending on if any enzyme function remains.
Those with one copy of a mutated gene typically
do not have symptoms. Many countries have
newborn screening programs for the disease.
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* PKU is caused by a genetic mutation (change
to the DNA) in the human phenylalanine
hydroxylase (PAH) gene.
There are many different types of mutations
that can affect the PAH gene, all of which
result in the body not producing a functioning
PAH enzyme.
Enzymes are proteins that speed up and
control chemical reactions. Lack of the PAH
enzyme means that a chemical called
phenylalanine, which is found in some foods,
can't be processed properly by the body.
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* All the genes in your body come in pairs. You
receive one half of the pair from your mother and
the other half from your father.
The mutation that causes PKU is an autosomal
recessive mutation. This means you need to
receive two mutated copies of the gene (one
from your mother and one from your father) to
develop the condition.
You won't develop PKU if you only receive one
mutated copy of the gene from one of your
parents, but you'll carry the mutated gene.
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PKU symptoms can be mild or severe and may include:
-Intellectual disability (formerly called mental retardation)
-Delayed development
-Behavioral, emotional and social problems
-Psychiatric disorders
-Neurological problems that may include seizures
-Hyperactivity
-Poor bone strength
-Skin rashes (eczema)
-A musty odor in the child's breath, skin or urine, caused by too
much phenylalanine in the body
-Fair skin and blue eyes, because phenylalanine cannot transform
into melanin — the pigment responsible for hair and skin tone
-Abnormally small head (microcephaly)
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*These include:
-eggs
-cheese
-nuts
-milk
-beans
-chicken
-beef
-pork
-fish
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To make sure that their body still receives an adequate amount of
protein, children with PKU need to consume PKU formula, which
contains all the amino acids that the body needs, except phenylalanine.
There are also certain low-protein, PKU-friendly foods that can be
found at specialty health stores. Children will have to follow the dietary
restrictions and consume PKU formula throughout their life to manage
their symptoms.
It’s important to note that PKU meal plans vary from person-to-person.
People with PKU will need to work closely with a doctor or dietitian to
maintain a proper balance of nutrients while limiting their intake of
phenylalanine. They’ll also have to monitor their phenylalanine levels
by keeping records of the amount of phenylalanine in the foods they eat
throughout the day.
Some state legislatures have enacted bills that provide some insurance
coverage for the foods and formulas necessary to treat PKU. Check with
your state legislature and medical insurance company to find out if this
coverage is available for you. If you don’t have medical insurance, you
can check with your local health departments to see what options are
available to help you afford PKU formula.
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* The United States Food and Drug
Administration (FDA) recently approved
sapropterin (Kuvan) for the treatment of
PKU. Sapropterin helps lower phenylalanine
levels. This medication must be used in
combination with a special PKU meal plan.
However, it doesn’t work for everyone with
PKU. It’s most effective in children with
mild cases of PKU.