By: Marki Wong

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Genetic testing for inherited Diseases -
Cystic Fibrosis

• By Marki Wong
• and
• Rebecca den Hollander

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What is Cystic Fibrosis?

• It affects the mucus glands, causing problems in
  the lungs and pancreas, leading to malabsorption
  and malnutrition it can also cause male
  infertility. Usually diagnosed in the first years
  of life.
• It is treated by focusing on clearing the airway,
  because 90 of affected individuals die from lung
  damage. The average life span is 30 years. Much
  milder forms of the disease are not detected
  until adult life.

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• Cystic fibrosis (CF) is a common autosomal
  recessive disease which mostly affects Caucasians
  of Northern European descent.
• The probability of having a child with Cystic
  Fibrosis is 1 in 2500 and there is a 1 in 25
  chance that you are a carrier.

Carrier Carrier
Carrier Unaffected
Affected Carrier
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Symptoms

• Thick, sticky mucus secretions in the lungs
• Repeated infections The accumulation of sticky,
  thick mucus in the lungs creates a favorable
  environment for infectious microorganisms to
  inhabit and grow.
• Feces is pale or clay colored, foul smelling, or
  floating
• Recurrent pneumonia
• Chronic cough, possibly with blood streaking
• Wheezing
• Bronchitis
• Chronic sinusitis
• Asthma
• Nasal polyps (fleshy growths inside the nose)
• Weight loss, failure to thrive in infants,
  abdominal swelling

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• Excessive salt in sweat, dehydration
• Failure of newborn to expel feces
• Abdominal pain, flatulence
• Fatigue
• Changes in color and amount of sputum (material
  coughed up from the lungs)
• Enlarged fingertips (clubbing)

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Carrier Testing for Cystic Fibrosis
The same test is then done on the fathers blood,
as both parents must be carriers in order to have
a child with Cystic Fibrosis. If the father and
mother are carriers, there are two tests which
can be performed on the fetus in order to find
out if they have Cystic Fibrosis.

• Firstly, the mother is tested to see if she is a
  carrier. This is done by karyotyping. 5 mL of
  room-temperature blood is taken and a solution is
  placed in the blood, called sodium heparin or
  ACD. If the gene, which is located on chromosome
  7, is mutated, she is a carrier.

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Pre-Natal Testing for Cystic Fibrosis

• Once both parents have tested positive as
  carriers of Cystic Fibrosis, the parents can
  decide to test the fetus, these tests can be
  performed
• CVS (chorionic villus sampling), a test where a
  catheter or needle is used to remove a piece of
  the placenta. This test can be done at 10-12
  weeks.
• Amniocentesis, where a needle takes fluid around
  the fetus to test it for the mutation.

This is done around the 16th week of pregnancy.
Early amniocentesis is the same test as
amniocentesis, except it can be done before the
15th week. Possibly between the 10th 14th week.
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Pros- for Prenatal Testing

• There are several pros for this genetic
  research. In the pre-natal testing, the parents
  have the ability to choose to continue with the
  pregnancy or not.
• Also, the preparation for having a child with
  Cystic Fibrosis is very difficult. Therefore, if
  the parents discover with this test that their
  child will have Cystic Fibrosis, it gives them
  time to come to grips with the consequences,
  emotionally, physically and economically.
• If the cost of testing is covered by your
  insurance company it is more likely that you
  would get the prenatal testing to be assured.

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Cons for Prenatal Testing

• The childs safety could be jeopardized in
  amniocentesis or CVS
• The test is not perfect and will not identify
  all carriers or fetus with Cystic Fibrosis
• If the cost of testing is not covered by your
  insurance company, it can be expensive to be
  tested.

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Would you want to know?

• There are many reasons why people choose to have
  genetic testing for cystic fibrosis and many
  reasons why people choose not to. Weve compiled
  a list of the pros and cons for being tested for
  cystic fibrosis.

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Why some people get tested

• They have a relative with cystic fibrosis.
• They are of an ethnic group that is at high-risk
  for carrying CF mutations.
• They would consider having prenatal testing
  (amniocentesis or CVS) if both partners are found
  to be CF carriers.
• They want information to prepare for having a
  child with special needs.
• They would use the information to help decide
  whether or not to continue a pregnancy.
• They think that their risk for being a carrier is
  high.
• Results would help them make important decisions
  about health and family.
• They can afford to pay for testing or know that
  testing is covered by insurance.

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Why some dont get tested

• They do not consider their risk for being a
  carrier high.
• They are not from an ethnic group that is
  considered high-risk.
• They would not use the information to make
  decisions, such as whether to have prenatal
  diagnosis (amniocentesis or CVS) or whether or
  not to continue a pregnancy.
• They know that the test does not look for all
  possible mutations, and that test results cannot
  entirely guarantee that someone is not a CF
  carrier.
• They cannot afford to pay for testing or do not
  have insurance coverage.
• They do not want test results in their medical
  record.

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So whats it like?

• We chose to do our presentation on cystic
  fibrosis because one of our families has been
  affected by this disorder, meaning that one of us
  is most likely a carrier. It is more common than
  people think and many will never realize that
  they are carriers.
• However, this research has only informed us we
  still have no idea what its actually like to
  have cystic fibrosis, so were conducting a
  little experiment ?
• Now imagine trying to concentrate in class when
  youre breathing like that most of the time.
  Imagine doing any type of exercise, or even just
  making a speech or presentation.
• Imagine living your life knowing that you will
  likely die by the age of 30.

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Bibliography

• http//esvc000625.wic021u.server-web.com/images/fa
  ctsheets/New20Cys.jpg
• http//www.horton.ednet.ns.ca/staff/selig/handouts
  /bio12/cellrepro/karyotype.pdf
• http//cystic-fibrosis-symptom.com
• http//www.questdiagnostics.com/hcp/intguide/jsp/s
  howintguidepage.jsp?fnTL_CysticFibrosis.htm
• http//www.labtestsonline.org/understanding/analyt
  es/cf_gene/test.html
• http//www.acog.org/from_home/wellness/cf001.htm
• http//hcd2.bupa.co.uk/images/factsheets/Cystic_fi
  brosis.gif
• http//www.dnadirect.com/tests/cystic_fibrosis/pro
  s_cons.jsp