Downs Syndrome



Downs Syndrome Etiology

The chromosomal defect trisomy 21 results in Downs syndrome.

  • 95% of cases are a result of nondysjunction or a cell division error during meiosis
  • the offspring of individuals carrying a Robertsonian translocation

The Robertsonian translocation involves

  • the long arm of chromosome 21q
  • with the long arm of one of the acrocentric chromosomes, A chromosome that has the centromere very near to one end (often 14 or 22)

The condition presents with a combination of birth defects:

  1. A degree of mental retardation
  2. characteristic facial features
  3. a variety of other health problems

Downs Syndrome Incidence

  • 1 in every 800 to 1000 births.
  • Risk increases with maternal age:
  • 1/1250 @ 25yrs old
  • 1/400 @35yrs
  • 1/100 @ 45 yrs
  • thought to reflect oocyte aging

Downs (prenatal screening tests) diagnostic tests

  • blood test to determine the probability of a woman giving birth to a Downs child
  1. maternal serum alpha-fetoproteins
  2. human chorionic gonadotropin
  3. unconjugated estriol
  4. inhibin A
  5. pregnancy associated plasma protein A
  • ultrasound for fetal nuchal translucency (increased in the Downs fetus)

Physical manifestations of Downs Syndrome

  • small square head
  • small nose
  • depressed nasal bridge
  • upward slanting eyes
  • small, low-set malformed ears
  • large protruding tongue
  • single simian palmar crease

Downs Syndrome Cognitive challenge and other functional compromises.

  • Language skills show a difference between understanding speech and expressing speech
  • Speech delays often require speech therapy
  • fine motor skill delay
  • Delayed walking onset

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