Phenylketonuria

1
Phenylketonuria
2
PKU

• PKU is a disorder caused by Recessive alleles.
• The Disorder is found on the 12th chromosome

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PKU Pedigree
4
How it is Inherited

• When a child is born with two copies of recessive
  alleles he inherits PKU
• Boys and girls are equally at risk of inheriting
  this disorder.
• Carriers are heterozygous for the trait
• The disease affects at least one of every 16,000
  babies, mostly those of northern European
  background. Jews, Asians, and Africans are less
  commonly affected.
• In this condition, an amino acid called
  phenylalanine builds up in the bloodstream,
  causing brain damage.
• In order for a child to inherit PKU, both parents
  must be PKU carriers.

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Diagnosis

• Nearly all cases of PKU in the United States are
  found in infant screenings
• The Doctor or nurse draws a small sample of blood
  and then a Technician tests the blood to see if
  the trait is present on the 12th chromosome.

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Symptoms

• Mental Retardation
• Behavioral and social problems
• Seizures tremors or jerking movements
• Rocking
• Hyperactivity
• Stunted Growth
• Skin Rashes
• Small head size
• Vomiting
• A musty odor in the skin, breath or urine caused
  by too much Phenylketonuria

The inability to change Phenylalanine Hydroxylase
to Phenylalanine causes all of these symptoms.
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Treatment

• A long life diet of a reduced protein diet is
  recommended to reduce build up of phenylalanine,
  but it can never be fully treated
• Kuvan is the first FDA approved drug for treating
  PKU.

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Life Expectancy

• Although PKU is a life-long disease, people who
  have PKU have the same average life expectancy as
  those who do not have the disease.

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Genetic counseling

• Genetic counselors have limited advice they can
  offer to people with PKU.
• Most genetic suggest a low or no protein diet
  depending on how sever the disease is.
  
• They may also suggest a special formula that
  delivers the amino acids the body is deprived of
  due to PKU.

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Interview

• - How common is it that you deal with this
  disease?  PKU is not that uncommon as far as
  genetic diseases go.  I dont know the exact
  incidence but you can look that up.  Most of the
  kids with PKU in houston are seen at our
  metabolic genetics clinic at TCH.
• -They are usually seen by the metabolic
  geneticist (MD), a metabolic nurse and a
  dietician. These specialists help coordinate
  their care and special dietary concerns and
  testing.
• -The diagnosis is almost always made on the
  newborn screening test.
• Sometimes the newborn screen is falsely abnormal
  which is why it is repeated and then a
  phenylalanine level is obtained.  If PKU is
  confirmed the baby is immediately started on the
  special diet.
• -Is this disease preventable by taking special
  precautions? The disease itself is not exactly
  preventable unless you do prenatal testing in a
  couple at risk.  However it is the bad effects of
  the disease that are completely preventable. 
• - Without the special diet and formula, people
  with PKU will have mental retardation.  If they
  stick with the diet, their intelligence is in
  normal range.
•  

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• 3. How must people living with phenylketonuria mod
  ify parts of their lifestyle? The biggest
  lifestyle adjustment is diet.  It depends on
  their phe level, but most classic PKU kids can
  have NO protein!
• Think about it, no cheese, no meat, no soda (look
  on the can). The diet is very restrictive and
  difficult to stick to as you can imagine. 
• To supplement, people with PKU also have to drink
  a special formula so they can get essential amino
  acids that they dont get in their diet.  I have
  never tasted this personally but I have heard
  that it is nasty!
•   You would think we could get it to taste good
  but no luck.  There are special companies that
  make foods like pasta and such for people with
  PKU also.  Frequent blood draws are also
  necessary to check Phe levels.
•  
• -What problems, if any, do people with
  phenylketonuria face later in life? Good
  question!  In the old days (10 years or so ago)
  we used to think that people with PKU could stop
  the diet when they reached adulthood (brain stops
  growing etc) however, many adults expressed
  difficulites when off diet.
• -They say they cant focus and have trouble with
  tasks and actually lose IQ points. So it seems
  the diet is important long term.  This is
  especially important for women. 
• -If a woman has PKU and becomes pregnant (off
  diet) her baby is at a very high risk to have
  mental retardation and other problems like very
  small head size. 
• -The baby does not have PKU but it is the effect
  of the high levels of phenylalanine in the mom's
  system that cross the placenta and hurt the
  baby.  So women with PKU should stay on the diet
  their whole lives and be especially vigilant when
  planning a pregnancy.
•  
• - Any other interesting facts about
  phenylketonuria?Other interesting facts  There
  is a new treatment being tried out for PKU (sorry
  dont remember the name). 
• - Also for kids in Texas with PKU we hold a camp
  every summer called camp Phever.  It is held at
  Camp For All and is a collaboration between the
  genetics groups at Baylor/TCH and UT/Hermann. The
  kids love it.

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Works CitedBatshaw, Mark L. "The Potential for
Gene Therapy in Inborn Errors of Metabolism A
Case Example" Pkunews.org. 1999. National PKU
News. 25 Jan. 2009 lthttp//www.pkunews.org/resea
rch/genether.htmgt. Calvin College Hekman Library
openURL resolver.Carter, Stien J. "Amino Acids
and Proteins" Biology.clc.uc.edu. 1996. 25 Jan.
2009 lthttp//biology.clc.uc.edu/courses/bio104/pro
tein.htmgt. Furman, Patti. "Fw Stratford Biology
Project (Interview)." E-mail to the author. 22
Jan. 2009. Hull, Janet S. "Phenylketonuria (PKU)
- Aspartame" Sweetpoison.com. 2002. Asparatame
Detox Program. 25 Jan. 2009 lthttp//www.sweetpoi
son.com/phenylketonuria.htmlgt."Phenylketonuria
(PKU)" Mayoclinic.com. 2007. Mayo Clinic. 25 Jan.
2009 lthttp//www.mayoclinic.com/health/phenylketon
uria/DS00514/DSECTIONsymptomsgt. Pku-info.org.
2006. 25 Jan. 2009 lthttp//fpwe.pku-info.org/index
.php?id16gt. "The Inborn Error of Metabolism in
PKU." Pku.com. 2007. BioMarin Pharmaceutical Inc.
25 Jan. 2009 lthttp//www.pku.com/AboutPKU/TheScien
ceOfPKU.aspxgt. "What is PKU?." Pkunetwork.org.
Children's PKU Network. 25 Jan. 2009
lthttp//www.pkunetwork.org/PKU.htmlgt.