2. Down Syndrome (trisomy 21 )
Introduction:
•Down syndrome is the most common chromosome abnormality in
humans.
• It is typically associated with a delay in cognitive ability (mental
retardation) and physical growth, and a particular set of facial
characteristics.
•The average IQ of young adults with Down syndrome is around 50,
compared to children without the condition with an IQ of 100.
•A large proportion of individuals with Down syndrome have a
severe degree of intellectual disability.

3. Def: is a numerical chromosomal abnormality caused by the presence of a third
copy of chromosome 21 (extra chromosme 21).
The extra chromosome causes problems with the way the body and brain develop.
Incidence: 1:700
Genetic types:
•During maternal meiosis[Resluting in ovum with 24
Non chromosomes (2 chromosomes21 instead of 1)]
disjunction(95%): •IQ is low & it’s mother age dependent.
•The extra chromosome is translocated to another
Translocation acrocentric chromosome.
(4%): •IQ is low & it’s not mother age dependent.
•One of parents should be translocation carrier.
•Post fertilization event.
Mosaicism(1%): •IQ is better.

5. Recurrence risk:
• Depend on mother age.
Non disjunction • Risk increase with advanced
maternal age.
• Depend on the chromosome to which the
“extra 21” is translocated
Translocation • To D- group (1/3 down _1/3 normal_1/3
carrier)
• To chromosome 21 (100% down)
mosaicism • minimal

6. Clinical picture:
Down syndrome symptoms vary from person to person and can range from mild to
severe. However, children with Down syndrome have a widely recognized
appearance.
1-Delayed mental and social development:
 Social smile ,Mother recognition, speech delay.
 Most individuals with Down syndrome have intellectual disability in the mild (IQ 50–
70) to moderate (IQ 35–50) range.
 Impulsive behavior
 Poor judgment
 Short attention span
 Slow learning
N.B Children and adults with DS are at increased risk for developing epilepsy and also
Alzheimer's disease.
2-Delayed motor development:
 Head support, sitting, crawling, walking, Fine motor skills are delayed.
 Some children will begin walking at around 2 years of age, while others will not walk
until age four.
 the development of gross motor skills affection is quite variable.

7. 3-characterstic dysmorphic features:-
Head & neck
 Skull:
Brachycephaly, delayed closure of AF, microcephaly
Separated joints between the bones of the skull (sutures)
 Hair:
silky
 Eye:
Upward slanting palpebral fissure
Medial epicathal fold
speckled iris(brushfield iris)
 Nose:
Depressed nasal bridge
Flattened nose
 Ears:
Small ears
Malformed, over folded helix
Underdeveloped ear lobule

8.  Mouth
Small mouth
Small oral cavity
Protruded & fissured Tongue
 Neck
short& broad
Excess skin at the nape of the neck
Hands , feet &abdomen
 Hands
short & broad hands
clinodactyly (incurved little finger)
simian crease (single transverse palmer crease)
 Feet
short & broad feet
wide gap between 1st & 2nd toes (sandal gap)
 Abdomen
distention & hernia

9. 4- Associated congenital anomalies:-
a) Cardiac: An atrioventricular septal defect also known as
endocardial cushion defect is the most common form with up
to 40% of patients affected, This is closely followed by
ventricular septal defect that affects approximately 35% of
patients.
b) GIT: duodenal atresia , annular pancreas, and imperforate
anus. Gastroesophageal reflux disease and celiac disease are
also more common among people with DS.
c) Renal anomalies

11. Complications:
a)cardiac: HF
b) Increaed risk of leukemia : In particular, acute lymphoblastic
leukemia at least 10 times more common in DS and the
megakaryoblastic form of acute myelogenous leukemia is at least
50 times more common in DS.
CHD Hypotonia
Leukemia(
decreased
immunity)
c)Chest
Recurrent chest infection

12. d) Thyroid disorders:
 Low thyroid (hypothyroidism) is most common, occurring in
almost a third of those with DS.
 This can be due to absence of the thyroid at birth (congenital
hypothyroidism) or due to attack on the thyroid by the immune
system.
e) Eye disorders: Almost half have strabismus.
Refractive errors, Cataracts, keratoconus ,and glaucoma.
f)Hip problems: risk of dislocation
g) Sleep apnea: because the mouth, throat, and airway are narrowed
h)Hearing problems: probably caused by regular ear infections.

13. Diagnosis:-
• Down syndrome can be identified in a baby at birth, or even before
birth by prenatal screening.
• A doctor can often make an initial diagnosis of Down syndrome at
birth based on how the baby looks. The doctor may hear a heart
murmur when listening to the baby's chest with a stethoscope.
 Lab:
• CBC
• Karyotyping : should be done in every patient to determine the
type & recurrence risk
 Imaging
• Echocardiogram to check for heart defects (usually done soon after
birth)
• ECG
• X-rays of the chest and gastrointestinal tract
• Abdominal US ( GIT & Renal anomalies)

15. Antenatal Diagnosis:
Indications:
• Old maternal age>35
• Previous baby with DS
• Family history of translocation
Methods:
1- Triple test: done in maternal serum at 15-16 weeks of gestation.
• ↓↓α-Fetoprotein
• ↓↓ Unconjugated estirol
• ↑↑β-hCG (Human chorionic gonadotropin)
Other Serum markers for Down's syndrome:-
• Pregnancy-associated plasma protein A (PAPP-A): levels reduced.
• Inhibin -A : raised levels.

16. 2-Fetal karyotyping:
• Amniocentesis: 14-16 weeks of gestation
• Chorionic villus sample: 9-12 weeks of gestation
3-Fetal US:
• Nuchal translucency ultrasound: thickening of the nuchal fold at
the back of the neck due to delayed drainage of fluid from the
upper part of the body
• Short femur ,Cystic hygroma of the neck& dudenal stenosis

18. Treatment:
There is no specific treatment for Down syndrome.
TTT of complications:
• A child born with a gastrointestinal blockage may need
major surgery immediately after birth. Certain heart
defects may also require surgery.

19. Supportive TTT:
• When breast-feeding, the baby should be well supported
and fully awake. The baby may have some leakage
because of poor tongue control. However, many infants
with Down syndrome can successfully breast-feed.
• Obesity can become a problem for older children and
adults. Getting plenty of activity and avoiding high-
calorie foods are important.
• Behavioral training can help people with Down
syndrome and their families deal with the anger, and
compulsive behavior that often occur. At the same time,
it is important to encourage independence.

20. • Special education and training is offered in most
communities for children with delays in mental
development.
• Speech therapy may help improve language skills.
• Physical therapy may teach movement skills.
• Special educators are also often needed.

21. Persons with Down syndrome need to be closely screened
for certain medical conditions.
They should have:
• Eye exam every year during infancy
• Hearing tests every 6 - 12 months, depending on age
• Dental exams every 6 months
• X-rays of the upper or cervical spine between ages 3 - 5 years [risk
of subluxation of atlantoaxial joint (C1-C2)]
• Thyroid testing every 12 months

22. Prevention:
• Genetic counseling for persons with a family history of Down
syndrome .
• The risk is significantly higher among women age 35 and older.
N.B American College of Obstetricians and Gynecologists recommends offering
Down syndrome screening tests to all pregnant women, regardless of age.

23. Thank you