HSN 107 Report: Genetic Basis and Management of PKU Disorder

This report provides a comprehensive overview of Phenylketonuria (PKU), a genetic disorder caused by a defective gene that leads to a deficiency in the enzyme responsible for processing phenylalanine. The report discusses the prevalence of PKU, noting its rarity and limited public awareness. It explains the genetic mutation in the PAH gene that causes the disorder, leading to a buildup of phenylalanine in the blood and potential brain damage. Clinical symptoms in newborns, including musty odor, neurological problems, skin rashes, and developmental delays, are detailed. The report also outlines diagnostic procedures, such as blood tests to detect excess phenylalanine, and emphasizes the importance of nutritional management through a restricted diet low in phenylalanine. The report concludes by highlighting the necessity of lifelong dietary restrictions and the consumption of specialized PKU formulas to manage the symptoms effectively.

Running head: PHENYLKETONURIA (PKU)
PHENYLKETONURIA (PKU)
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PHENYLKETONURIA (PKU)
Overview of the Disease:
A defective gene caused by genetic mutation is the main cause of the Phenylketonuria
(Pku) disorder that can be in the intensity of mild, moderate and severe. In the persons who are
affected by the disorder, the defective genes result in the lacking or the deficiency of the enzyme
which rakes active part in the processing of the phenylalanine (which is an amino acid). Often a
dangerous build up of this protein can take part because the enzyme cannot function successfully
(1). When such individuals take in protein rich foods like that of milk, nuts, cheese, milk and
other grains like bread and pasta, aspartame and artificial sweetener, the protein buildup further
intensifies. This build up of the protein ultimately cause damage in the nerve cells in the brain.
Therefore, when they are diagnosed with the disorder, they have to strictly maintain their diets
that need to have limits on the protein phenylalanine (2).
Prevalence:
The Phenylketonuria (Pku) is a rare genetic disorder that is mainly seen to affect one in
every 10000 Australian babies. The knowledge of the Australian about the disorder is very
limited. The parents are only seen to have heard the name of the disorder when their babies are
undergone the Guthrie test (a heel-prick blood test) after they are born or from the
“phenylketonurics warning” label that they found on the surface of some of the diet drinks.
However, they still seem to develop no ideas about the disorder (3).
Genetic mutation:
Mutation in the PAH gene mainly results in the occurrence of the disorder. The PAH
gene mainly helps in providing various forms of instructions for making of the enzyme called the
phenylalanine hydroxylase. This enzyme is helpful in the conversion of the amino acids namely

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phenylalanine to different types of compounds within the systems. When the gene mutations
affect the gene, it causes reduction in the activity of the enzyme and therefore the protein namely
phenylalanine cannot be processed from the diet. In the course of time, the amino acid is seen to
be built up in the in the blood and other tissues in toxic levels (4). The nerve cells in the brain are
particularly sensitive towards the phenylalanine levels and therefore, their excessive amounts of
this substance can cause brain damages. Studies are of the opinion that classic PKU, which is the
most rigorous form of the disease, is seen to occur when the enzyme phenylalanine hydroxylase
activity become severely impaired or remains totally absent. People who are not treated properly
when they get affected by the disorder are seen to have high levels of phenylalanine that can in
turn cause severe types of brain damage as well as other serious types of the health problems.
For an infant to inherit the disorder, the mother as well as the father needs to have and
pass on the defective gene. This pattern of the inheritance is called the autosomal recessive. It is
possible for the parent to be a carrier of the defective gene that causes the disorder but may not
possess the symptoms of the disorder (5). If only one parent has the defective gene, the child will
not be affected. If both the parents have the defected gene and the pass them to the child, the
child will have two copies of the gene and this would result in the development of the disorder.
Clinical symptoms:
Newborn babies with the disorder do not have any symptoms. If they are not treated on
time, the babies are seen to develop signs of the disorder within a few months. One of the most
important sign is the presence of the musty odor in the breath as well as in the skin or urine and
this is mainly caused by a high level of the compound of phenylalanine in the body (6).
Moreover, neurological problems might be also seen to occur that ultimately result in including

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seizures. Moreover, it also raises skin rashes and results in the occurrence of the eczema.
Moreover, fair skin and blue eyes are also seen to occur because the protein cannot transfer
melanin that is the pigment that is responsible for hair and skin tone. Moreover, the individuals
are also seen to be suffering from abnormally small head called the microcephaly. The disorder
also results in development of hyperactivity in the affected individuals. Other signs and
symptoms that are also included are the intellectual disability and even the delayed development.
It also results in various types of emotional, social and behavioral problems. Such individuals are
also seen to suffer from psychiatric disorders.
Diagnosis:
The test for PKU is mainly done within two days after the baby is born. The test is
mainly done after the baby is at least 24 hours old and after the baby had been given the scope of
ingesting some proteins in the diet for ensuring the accurate results. Mainly, the nursing
healthcare professional or the lab technician is seen to be collecting a few drops of blood mainly
from the heel portion of that of the baby or from the bend in the arm of the baby. Moreover, the
laboratories are also seen to test the sample of blood drops to find out whether the patient is
affected or not. The tests mainly help in searching for the presence of the protein in excess
amount in the blood (7). Moreover, additional tests are also performed to confirm the initial
results. The tests help to find out the presence of the PAH gene mutation which causes the PKU.
These tests are mainly done within the six weeks after birth.
Nutritional management:
The main procedure for the treatment of the disorder is eating a particular diet that
confines the intake of foods that contain phenylalanine. Children who are suffering from the

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disorder can be fed breast milk. These children can also consume a specific type of formula
known as the Lofenalac. When the baby becomes old enough to be capable of eating solid foods,
the caregivers should make them avoid eating of foods that are high in protein. These forms of
the foods are seen to include cheese, milk, eggs, nut, milk, beans, beef, chicken, fish as well as
pork. In order to ensure that they are still receiving sufficient quantity of protein, infants with
the disorder need to consume a specific type of PKU formula. This formula consists of all the
protein that the body needs accept that of the phenylalanine. Many of the low protein, PKU
friendly foods are found at the specialty health stores (8). People who suffer from this disorder
have to follow as their dietary restrictions as well as consume PKU formula for the rest of their
lives for effectively maintaining their symptoms.

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2017 Dec;18(1):603.
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