Down's Syndrome

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Mechanisms:

94% non-dysjunction at anaphase I or II

3-4% translocation

2-3% Mosaicism (germline or gonadal)

Typically a spontaneous event, unless caused by a translocation.

To calculate recurrence risk must take into account:

Maternal age

Previous history (more likely if previously had children with T21)

Karyotype of previously affected child

Parental karyotype

Nuchal Translucency Scan

Can be carried out during the dating scan (ultrasound) 11-14 weeks

In combination with a blood test and maternal age can work out whether pregnancy is high risk

Quadruple Blood Test

14-20 weeks gestation. 82% accuracy.

If shown to be high risk on either of these tests can have CVS (11-14 weeks) or amniocentesis (15-20 weeks)

Characteristic appearance - facial, short stature

Personality - friendly, no sense of danger

LD/DD

Hypotonia

Higher risk of infections

Heart defects

Leukaemia

Mental Health Problems - Autism

Epilepsy

Alzheimer's

Eye problems - cataracts, eyes don't move together

Hearing problems

Low thyroid

Constipation

Clinical Features

inheritance

Genetics

tests