1 in 650 to 700.

This condition derives its name from Dr. Langdon Down ,who first described it in the clinical lecture reports of the London hospital in 1866.

•Abnormality •Frequency (%)Trisomy 21.(nondisjunction of chr.-21 in maternal meiosis – 1).

95

Robertsonian translocation –D/G-(21q/21q , 22q/21q )

4

Mosaicism(Often less severely affected than those with full syndrome.)

1

0

20

40

60

80

100

Category 1Category 2

Category 3

Series 1

Series 2

Series 3

•Cause •Recurrencerisks

Trisomy 21 1/200 to 1/100

Translocation Male:1-3%Female:10-15%

Translocation between 21q & 21q

100%

Newborn period: Hypotonia , sleepy excess nuchal skin .

Craniofacial: Brachycephaly ; epicanthic folds & brush-field spots on eye ; upward sloping palpebral fissures ; protruding tongue ; small ears ; flat nasal bridge .

Limbs: Single palmar crease ( “simian crease” ) , small middle phalanx of 5th finger , wide gap between 1st & 2nd toes .

Cardiac: Atrial & ventricular septal defect ; common atrioventricular canal ; patent ductus arteriosus .

Others: i)Anal atresia , duodenal atresia , Hirsch-prung disease.

ii)Short stature , strabismus .

iii)Average I.Q. of young adults is around 40 to 45 .

iV)Social skills well-developed , most of the children are happy & very affectionate .

They are susceptible to infection & often have congenital heart disease ( in about 50% of all cases ). So , they usually die young . Generally they have a lifetime of about 40 – 50 years , except in severe cases .

i) High resolution USG.

ii) Chorionic villus analysis .

iii) Cultured amniotic cells .

iv) FISH technique .

v) Prenatal screening programmes have been introduced based on the so called “triple” or“quadruple” tests of maternal serum at 16 weeks’ gestation .

Questions?

Questions?Questions?

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