Down's Syndrome (1)

Question 1

What is it caused by?

How does it present?

Answer 1

➊ Trisomy 21

➋ • Hypotonia
• Brachycephaly – small head with flat back
• Upward sloping palpebral fissures (eye lids)
• Single palmar crease
• Prominent epicanthic fold (fold on upper eye lid)
• Short neck
• Short stature
• Flattened face and nasal bridge

Question 2

What are its complications?

Answer 2

• LD
• Hearing problems
  ‣ Recurrent otitis media, Glue ear (Otitis Media with Effusion)
  ‣ Deafness, Eustachian tube abnormalities
• Visual problems such as myopia (short-sightedness), strabismus, cataracts
• CHD particularly ASD, VSD, PDA, ToF
• Hypothyroidism
• Atlantoaxial instability
• Leukaemia and Alzheimers Dementia more common

N.B. The APP (amyloid precursor protein) gene responsible for Alzheimers is also on chromosome 21. So trisomy 21 leads to more APP, therefore a greater risk of AD.

Question 3

Screening:
What is it like for pregnant women?

What is the 1st line test done?
→ At which wk is it done?
→ What does it involve?

Answer 3

➊ All offered screening for Down’s to know if more invasive tests are needed for a definitive diagnosis

➋ Combined Test
→ 11-14 wks
→ • US – Measure nuchal translucency – Will be thicker (>6mm) in Down’s
• Blood test
‣ Beta-hCG – higher level indicates greater risk
‣ PAPPA – lower level indicates greater risk

Question 4

Testing:
If the screening test indicates a greater risk, how is the foetal DNA tested?

What is involved in the Non-invasive Testing?

Answer 4

➊ • Chorionic Villus Sampling (CVS) – US-guided biopsy of placental tissue – Used if < 15 wks
• Amniocentesis – US-guided aspiration of amniotic fluid – Used if > 15 wks once there’s enough amniotic fluid to make sampling safer

➋ Blood taken from mother, and fragments of foetal DNA are taken and analysed – Not definitive but gives a very good indication of Down’s, and may be preferred to the more invasive methods of CVS and amniocentesis

N.B. Even if NI testing is +ve, Invasive tests will still need to be done for a definitive diagnosis

Question 5

How is it managed?

Answer 5

• Echo
• Regular hearing tests
• Regular eye tests
• Regular thyroid checks