Down Syndrome
Contents
• What is down syndrome
• Karyotype
• Incidence
• Mechanism
• Sign and symptoms
• Diagnosis
• Screening
• Management
• Prognosis
What is down syndrome
• Named after British doctor John Langdon Down, who fully described the
syndrome in 1866
• Down syndrome is the most common chromosome abnormality in
humans
• Also known asTrisomy 21
• 92-95 %cases by the karyotype 47,XX,+21 for females and 47,XY,+21
for males,Caused by a failure of the 21st chromosome to separate during
egg or sperm development (nondisjunction)
• 1.0 to 2.5% of cases, some of the cells in the body are normal and others
have trisomy 21, known as mosaic Down syndrome.
• The extra chromosome 21 material may also occur due to
Karyotype
Incidence
• The incidence of Down syndrome in live births is approximately 1 in
733.
• The incidence at conception is more than twice that rate; the difference is
accounted for by early pregnancy losses.
• Maternal age affects the chances of having a pregnancy with Down
syndrome.
• At age 20, the chance is 1 in 1,441
• at age 30, it is 1 in 959
• at age 40, it is 1 in 84
• at age 50 it is 1 in 44.
• Although the probability increases with maternal age, 70% of children with
Mechanism
• The extra genetic material present in DS results in
overexpression of a portion of the 310 genes located on
chromosome 21.
• This overexpression has been estimated at around 50%, due to
the third copy of the chromosome present.
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Signs and symptoms
Signs and Symptoms
Diagnosis
• Before birth
• amniocentesis ( not recommended before 15 weeks gestational age )
• chorionic villus sampling (not before 10 weeks gestational age)
• After birth
• The diagnosis can often be suspected based on the child's physical appearance
at birth.
• An analysis of the child's chromosomes is needed to confirm the diagnosis
• Screening
• Guidelines recommend screening for Down syndrome to be offered to all
pregnant women, regardless of age
Screening
Management
• There is no cure for Down syndrome.
• Education and proper care have been shown to improve quality of
life such as
• Typical childhood vaccinations
• electrocardiogram and ultrasound of the heart. Surgical repair of
heart problems may be required as early as three months of age.
• checking the person's testicles yearly
• Hearing aids or other amplification devices can be useful for
language learning in those with hearing loss.
• Speech therapy may be useful and is recommended to be started
around nine months of age.
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• Tympanostomy tubes are often needed
• Tonsillectomy is also often done to help with sleep apnea
and throat infections.
Prognosis
• Individuals with Down syndrome have a higher risk of early
death than the general population.
• This is most often from heart problems or infections.
• In those with congenital heart problems, 60% survive to
10 years 50% survive to 30 years of age. In those without heart
problems, 85% survive to 10 years and 80% survive to 30 years
of age. About 10% live to 70 years of age.
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