Downs Syndrome Flashcards
What is the most common aetiology of downs syndrome and what is the major risk factor?
Most commonly (94%) due to meiotic non disjunction
Aka chromosome 21 fails to split during meiosis so the gamete has 2 copies when it combines with a normal gamete in fertilisation there is a trisomy 21.
The greatest risk factor is age. Incidence increases greatly with mothers over 30.
Note: paternal age is also important.
What are the dysmorphic features which are seen in downs syndrome?
Face and head:
- Brachycephaly (small/short skull)
- Epicanthic folds (slanted eyes)
- Brushfield spots (white/grayish/brown spots on the periphery of the iris)
- Low set ears
- Flat nasal bridge
- Protruding tongue
Neck:
-Loose skin on back of neck
Hands and feet:
- Single palmar crease
- Large gap between hallux (big toe) and second toe
Small stature
What are the other common abnormalities seen in downs syndrome?
Learning difficulties (always present to a varying degree)
Congenital heart defects (AVSD is very rare in children without downs, note VSD is still the most common heart defect)
Duodenal and oeseophageal atresia
Which diseases are associated with downs?
Eyes:
Cataracts
Refractive errors
Endocrine:
Hypothyroidism
Gastro:
Hirschsprung’s
Coeliac
Meckel’s diverticulum
MSK:
Scoliosis
Foot deformities
Haematological:
Increased risk of infection
Increased risk of ALL and AML
What are the investigations to dectect downs?
COMBINED TEST ANTENATALLY (11-13+6 weeks):
Increased nuchal translucency on USS
Bloods show reduced Papp-A and increased HcG (11-13 weeks)
If combined test can’t be down triple test (bloods) done from 14-20 weeks
Showss increased beta-hCG, reduced alpha fetoprotein (AFP), increased inhibin-A and reduced estriol (uE3)
Diagnosed with amniocentesis or CVS a few weeks later
If not tested for in utero can be tested for using FISH (fluorescent in situ hybridisation) techniques on a blood sample.
