Down’s syndrome(an

UPDATE)

SAYAN BANERJE

E

Incidence 1 in 650 to 700.

Nomenclature This condition derives its name from

Dr. Langdon Down ,who first described it in the clinical lecture reports of the London hospital in

1866.

Chromosomal basisAbnormality 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

TRISOMY 21 ROBERTSONIAN TRANSLOCATION

MOSAICISM0

10

20

30

40

50

60

70

80

90

100

Series 1

Graphical representation of

chromosomal basis

Recurrence risks

•Cause •Recurrence risks

Trisomy 21 1/200 to 1/100

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

Translocation between 21q & 21q

100%

Clinical featuresNewborn 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: Anal atresia , duodenal atresia , Hirsch-prung disease. Short stature , strabismus . Average I.Q. of young adults is around 40 to 45(RANGE→20-50) . Social skills well-developed , most of the children are happy & very

affectionate . May be associated with ALL & AML(M7) . Antibody against thyroid may develop- Autoimmune Thyroiditis.

Average lifetime

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 .

Prenatal diagnosis 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 .

Diagnosis by FISH technique

KARYOTYPE

Epicanthic foldFlat nasal bridgeProtruding tongue

Karyotype:Trisomy 21 Robertsonian translocationMosaicism

Simian crease

Brushfield spotsEpicanthic fold

Short ear

Protruding tongue

Large gap between 1st & 2nd toes

BRUSHFIELD SPOTS

KERATOCONUS

Questions?

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