2. INTRODUCTION:
• Phenylketonuria (PKU) is a genetic condition that is present from
birth. In this the body is unable to break down a substance called
phenylalanine, which builds up in the blood and brain. Hepatic
enzyme phenylalanine hydroxylase (PAH) is necessary to
metabolize the amino acid phenylalanine (PHE) to the amino acid
tyrosine. When PAH activity is reduced, phenylalanine
accumulates and is converted into phenyl pyruvate (also known
as phenyl ketone), which can be detected in the urine.
3. DEFINITION:
• Phenylketonuria (PKU) is an autosomal recessive metabolic
genetic disorder characterized by a mutation in the gene for
the hepatic enzyme phenylalanine hydroxylase (PAH),
rendering it non-functional.
4. INCIDENCE:
• PKU is rare – it is estimated to affect 1 in every 10,000
babies born in the UK.
• Both sexes are affected equally by PKU.
• The condition is slightly more common in white people.
5. CAUSES:
• Genetic mutation: The mutation in the gene causes the
condition. The defective gene contains the instructions for
making an enzyme needed to process the amino acid called
phenylalanine.
• For a child to inherit PKU, both the mother and father must
have and pass on the defective gene. This pattern of
inheritance is called autosomal recessive.
6. • PKU is passed to children by parents who are
carriers of the disorder, but don't know it.
7. RISK FACTORS
• Both parents must pass along a copy of the mutated PKU
gene for their child to develop the condition. If only one
parent has the PKU gene, there's no risk of passing PKU to a
child.
• Children of mothers who have PKU but who didn't follow
the PKU diet during pregnancy also may be affected.
Although these children don't often have PKU, they do have
serious consequences of the high level of phenylalanine in
the mother's blood.
8. Clinical manifestation:
• Newborn with phenylketonuria initially don't have any symptoms.
Phenylketonuria symptoms can be mild or severe and may
include:
• Mental retardation.
• Behavioral or social problems.
• Seizures, tremors or jerking movements in the arms and legs.
• Hyperactivity.
• Stunted growth.
• Skin rashes (eczema).
9. • Small head size (microcephaly).
• Fair skin and blue eyes, because phenylalanine cannot
transform into melanin — the pigment responsible for hair
and skin tone.
• The most severe form of the disorder is known as classic
PKU. Children with untreated classic PKU usually develop
obvious, permanent mental retardation.
• Epilepsy (50%)
• Eye abnormalities (eg. hypo pigmentation)
10. DIAGNOSTIC EVALUATION
• Newborn blood testing identifies almost all cases of PKU.
• In case of family history of PKU, the physician may
recommend screening tests before pregnancy or birth. It's
possible to identify PKU carriers through a blood test.
• Perform screening on blood samples during the first week of
life.
11. • Results of urine tests (i.e. ferric chloride test) may be
negative in the first month of life and are rarely used in
current practice. Perform blood and urine analysis of
biopterin and neopterins to exclude defects of biopterin
synthesis or recycling.
• Screening for PKU: Babies can be screened by the heel prick
test and it should be carried out during the first week of a
baby’s life.
12. Management:
• Medical management:
• The drug sapropterin (Kuvan) can be given for the treatment
of PKU.
• Dietary modifications:
• The main treatment for PKU is a low-protein diet that avoids
foods such as meat, eggs and dairy products, and controls
the intake of many other foods (such as potatoes and
cereals).
13. • In addition, amino acid supplements should be given to
ensure that the patient is getting all of the nutrients
required for normal growth and good health.
Phenylketonuria (PKU) can be successfully treated with a
low-protein diet and dietary supplements.
• Fresh fruits – with the exception of bananas, figs and dates
14. • Most vegetables – with the exception of asparagus, bean
sprouts, broccoli, Brussels sprouts, and cauliflower
• There are also a number of specially designed low-protein
versions of popular products, such as flour, rice and pasta
specifically designed for people with PKU and related
conditions.
15. Amber foods like:
• Cornflakes.
• Chips.
• Baked beans.
• Milk – a specially designed formula can be used as a milk
substitute for babies and children.
• Rice.
Formula for babies
• The Phenylalanine-free infant formula should be given to the
baby.
16. COMPLICATIONS:
• Untreated PKU can lead to:
• Irreversible brain damage.
• Marked mental retardation may occur within the first few
months of life.
• Behavioural problems and seizures in older children.
• Psychological problems, including poor self-esteem,
agoraphobia.
