Genetics - Down's Syndrome

Question 1

What are the physical features of Down’s Syndrome?

Answer 1

Hypotonia
Brachycephaly
Prominent epicanthic folds
Flattened face and nose
Upward sloping palpebral fissures
Short neck
Short stature
Single palmar crease

Question 2

What are epicanthic folds?

Answer 2

Folds of skin covering medial portion of eye

Question 3

What are palpebral fissures?

Answer 3

Gaps between lower and upper eyelid

Question 4

What is brachycephaly?

Answer 4

Small head with a flat back

Question 5

What are the complications of Down’s Syndrome?

Answer 5

Learning disability
Recurrent otitis media
Deaness
Visual problems
Hypothyroidism (10-20%)
Cardiac defects 1/3
Atlantoaxial instability
Leukaemia
Dementia

Question 6

Why is deafness a complication of Down’s Syndrome?

Answer 6

Eustachian tube abnormalities

Leads to glue ear and conductive hearing loss

Question 7

What visual problems might a child with Down’s Syndrome have?

Answer 7

Myopia
Strabismus
Cataracts

Question 8

What cardiac defects affect children with Down’s Syndrome?

Answer 8

ASD
VSD
PDA
ToF

Question 9

What is the first line test for antenatal screening of Down’s Syndrome?

Answer 9

Combined test
Most accurate and test of choice where possible

Combination of USS and maternal blood tests

Question 10

What does the Combined test, test for?

Answer 10

USS
Measures nuchal translucency
Over 6mm thickness indicates DS

Maternal blood tests
- Beta-HCG (higher indicates greater risk)
- Pregnancy-associated plasma protein-A (PAPPA) (lower result indicates greater risk)

Question 11

What is the triple test?

Answer 11

Only involves maternal blood test results

Beta-HCG (higher indicates greater risk)
Alpha-fetoprotein (AFP) (lower indicates greater risk)
Serum oestriol (lower indicates greater risk)

Question 12

When is the triple test performed?

Answer 12

14-20 weeks of gestation

Question 13

What is the quadruple test?

Answer 13

Exact same as triple test, also includes inhibin-A, higher inhibin-A indicates higher risk

Question 14

How is risk score for DS calculated?

Answer 14

Antenatal screening tests

Question 15

When risk of DS is greater than 1/150 what is offered?

Answer 15

Amniocentesis or chorionic villus sampling

Result occurs in around 5% of women

Question 16

What does amniocentesis or chorionic villus sampling involve?

Answer 16

Sample of foetal cells which then undergo karyotyping to give a definitive answer

Chorionic villus sampling
- USS guided biopsy of placental tissue
- Used before 15 weeks of pregnancy

Amniocentesis
- USS guided aspiration of amniotic fluid
- Later in pregnancy once enough amniotic fluid to make sampling safer

Question 17

What is Non-invasive prenatal testing? (NIPT)

Answer 17

New test for detecting abnormalities in foetus during pregnancy

Blood test from mother

Blood contains DNA fragments which come from placenta and foetal DNA

Fragment analysed and detect Down’s

Not definitive but very good indication

Question 18

How is DS managed?

Answer 18

Need support from MDT to meet needs
- Occupational therapy
- SALT
- Physiotherapy
- Dieticians
- Paediatricians
- GP
- Health visitors
- Cardiology for congenital heart diseases
- ENT for ear problems
- Audiology for hearing aids
- Opticians for glasses
- Social services for social care and benefits
- Additional support with educational needs
- Down’s Syndrome Association charity

Question 19

What routine investigations are important for children with DS?

Answer 19

Regular thyroid checks (every 2 years)
Echocardiogram for cardiac defects
Regular audiometry
Regular eye checks

Question 20

What is the prognosis of DS?

Answer 20

Average life expectancy is 60