Download Kate is born with features that do not look quite normal. Her eyes are

Kate is born with features that do not look quite normal. Her eyes are wide-set, and slightly slanted. Her nose is
short and flat, and she keeps her mouth slightly open. There is a straight crease across her palm, and her fifth digit
is unusually short. The doctor tells her parents she has an inherited disorder.
What is the doctor's diagnosis?
What is the prognosis?
The doctor warns Kate's parents of several possible complications. List these with an explnation of the prognosis for
each.
What is the etiology of Kate's disorder? How does this happen
What are the risk factors for bearing a child like Kate?
What are the issues associated with genetic counseling?
What are the issues associated with testing for genetic diseases during pregnancy? (Amniocentesis & Chorionic
Villis Sampling)
The doctor’s likely diagnosis for Kate is a common genetic abnormality called Down syndrome. Certain physical
characteristics are present in most children with this disorder and have varying degrees of severity and prevalence.
Most children who were not diagnosed in utero are initially diagnosed based on physical appearance after birth.
Further genetic testing should be done to confirm the suspected diagnoses. Some of the physical features of Down
syndrome include flattened face and nose, slanted eyes, small often gaping mouth, protruding tongue, small ears,
short neck, white spots on the iris, small broad hands with a lateral crease, and a short curved fifth digit. Since Kate
possesses several key physical attributes associated with this disorder, the doctor will likely diagnose her with Down
syndrome.
There is no known cure for Down syndrome though many of the problems associated with this disorder are
treatable. Recent advances in medicine have significantly increased the lifespan of individuals with Down
syndrome. In 1912 the average lifespan of a child with this disorder was just 12 years. By 1983 this number had only
increased to 25 years. Today’s affected children are expected to live to age 55 and beyond. Joyce Greenman is the
oldest woman living with Down syndrome at 87 years old. In addition to increased lifespan the quality life of those
with Down syndrome has greatly improved. These individuals complete high school, participate in sports, and have
rewarding volunteer or paid jobs.
Children with Down syndrome have many serous potential complications. However, a large portion of these
medical conditions can be treated. Listed below are several complications associated with this disorder.
Cognitive impairment: Intellectual, social, and emotional development is impaired in nearly all those affected by
Down syndrome. The level of impairment is reliant on the individual child and varies greatly. For this reason
prognosis is greatly dependent on the individual and is often difficult to predict. Children commonly develop
milestones such as talking and walking at a much slower pace. IQ tests reveal scores that are frequently half of those
without Down syndrome. Success in school also varies greatly.
Congenital heart disease: Nearly 50% of babies born with Down syndrome have heart defects. The principal
defect associated with these children is called an atrioventricular septal defect. This is a hole in one of the walls of
the heart or an abnormality with a valve. This malformation causes mixing of the contents of each heart chamber
and reduces the efficacy of the heart. This defect can be treated with drugs and repaired through surgery. Prognosis
is very favorable with surgery survival percentages in the high 90’s.
Leukemia: Children with Down syndrome have a 10 to 20 time greater chance of developing leukemia. The
reason behind this phenomenon is not yet understood. Leukemia is a cancer of blood cells. There are several forms
of leukemia though the most common in children with Down syndrome is acute lymphoblastic leukemia. This
rapidly progressing cancer can become fatal in just a few weeks if left untreated. This type of cancer can be treated
with chemotherapy, radiation, bone marrow transplants, and several other methods. Prognosis can be anywhere from
25%-75% survivability. New advancements in treatment therapies are continually increasing survivability rates.
Additional potential complications include cancer, celiac disease, hypothyroidism, cervical spine instability, sleep
apnea, seizures, hearing loss, visual impairment, early-onset Alzheimer’s disease, autism, ADHD, and depression.
The etiology behind Kate’s condition is a genetic abnormality known as trisomy 21. Each cell in our body
normally contains 23 pairs of chromosomes. Down syndrome occurs when chromosome 21 receives a third
chromosome. This extra genetic information on chromosome 21 causes all of the abnormalities associated with
Down syndrome. There are three different pathways for the third chromosome 21 to attach.
The first and most common method in which trisomy 21 occurs is through the nondisjunction of germ cells. This
event takes place during oogenesis when chromosome 21 does not separate during division. The outcome is an
ovum containing an additional chromosome 21. When a sperm combines with this ovum the product is a zygote
with a triple dose of chromosome 21.
Trisomy 21 also occurs in a very similar manner with the main difference being the nondisjunction occurs in a
zygote instead of a single germ cell. This happens when chromosome 21 does not separate in division of the zygote.
This results in only one portion of the cells being affected and the other portion remains normal. This is sometimes
called mosaic Down syndrome because it represents a mixture of two dissimilar types of cells. Individuals affected
by this type of Down syndrome usually have a less severe manifestation of the disorder.
The third way trisomy 21 takes place is through translocation. During meiosis chromosomes can sometimes break
and fuse with another chromosome. In this event chromosome 21 breaks and typically fuses to chromosome 14. The
end result is still a fertilized ovum with an extra chromosome 21.
The greatest known risk factor for Down syndrome is increased age. The incidence of Down syndrome
drastically enlarged with age. A woman who is over 40 can have as high as a 2% chance of bearing a child with
Down syndrome. Another risk factor is a mother who previously gave birth to a child affected by Down syndrome.
Additionally, parents who are carriers of the genetic translocation for Down syndrome have a greater probability of
conceiving a baby with Down syndrome.
I believe one of the most fascinating issues regarding genetic counseling is testing DNA for predisposition of
late-onset diseases. In the future we will most likely be able to test for an individual’s predisposition to our nation’s
leading causes of death such as heart disease, stroke, and respiratory diseases. Scientists can already test for
disorders such as Huntington disease, certain cancers, and polycystic kidney syndrome and it’s only a matter of time
before they discover effective tests for more disorders. The issue I see with testing is the benefit or lack thereof
regarding knowing the outcome of such tests. Today’s Americans are more educated about health than ever before,
yet our leading cause of death is still heart disease. While genetics do play a role in developing heart disease, I
believe for most people environmental factors such as diet have a larger impact on our hearts than genetics. We
know that cheeseburgers and french fries can eventually lead to a heart attack yet we continue to consume fast food
meals. If a person knew they were predisposed to a disease what impact would it have on their health? I believe this
sort of testing would be beneficial to some, but wouldn’t change a thing for most.
I believe one of the most evident issues regarding testing for genetic disease during pregnancy is its limitations.
Many mothers elect to perform genetic testing during higher risk pregnancies to determine potential complications.
The two main types of genetic testing are amniocentesis and chorionic villus sampling. During amniocentesis a
syringe is used to draw out amniotic fluid and cells within the fluid are tested. During Chorionic villus testing a
small tissue sample is suctioned from the placenta and used to perform tests. Scientists then determine the genetic
likelihood of certain disorders. While genetic testing can be used as a very effective tool, there are limitations.
Genetic testing cannot always predict the severity of the potential problem. Fetuses are commonly checked for the
cystic fibrosis gene which may be expressed as severe life threatening respiratory problems or produce much more
benign symptoms. Other genes may be identified that show an increased risk for certain disorders, but does not
guarantee their emergence. This information brings a great deal of uncertainty to the future health of the child, and
the future decisions of parents.