down’s syndrome an update
TRANSCRIPT
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?
Questions?Questions?
Questions??