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Flashcards in Downs syndrome Deck (12)
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1
Q

What are risk factors for down syndrome?

A
  • increasing maternal age
  • previous child with down syndrome
2
Q

Describe the clinical features of down syndrome

A
  • clinical heart defects
  • Mental retardation (IQ 30-60), higher risk of alzheimers
  • Increased risk of Leukemia
  • Middle phalange of the 5th finger is shorter than normal, causing fifh finger clinodactyly (curvature basically)
  • Flat face
  • Protruding tungue
3
Q

What is the life expectancy of someone with down syndrome?

A

50 years

4
Q

Are people with down syndrome infertile?

A

Sometimes. Women with down syndrome give birth to children with down syndrome 40% of the time.

5
Q

A downs syndrome screening can be slightly different depending on how far along the pregnancy is. One is before 14 weeks, whilst the other can be between 14-20 weeks. State what each test consists of.

A

< Week 14: Blood test and Nuchal Translucency scan

Weeks 14-20: Blood test

6
Q

Explain what the Nuchal translusency test is for downs syndrome screening

A
  • Ultrasound scan
  • Measures the translusency of the collection of fluid under the skin at the back of the fetus’ neck
7
Q

Describe what blood tests are measuring in downs syndrome screening

A
  • PAPP-A (Pregnancy assoicated plasma protein A) - this is typically lowered in downs syndrome children
  • Free levels of HCG being increased is possible marker of downs syndrome
8
Q

Screening tests can only indicate the likelyhood or chances that a mother is carrying a baby with Down syndrome. What are they main diagnostic tests for down syndrome?

A

Chorionic Villus sampling

Amniocentesis

9
Q

Describe amniocentesis

A
  • Sampe of fluid that bathes the fetus is withdrawn through a needle inserted in through the mother’s abdominal wall then into the uterus
  • Sample is then used to analyse the chromosome of the fetus
  • Low risk of miscariage
10
Q

Describe chrionic villus sampling

A

A catheter is guided through the vagina, cervix and then advanced to the chorionic villi (which contain the fetal capillaries under ultrasound guidance)Tissue is taken to test for chromosomal abnormalities.

11
Q

Explain the pathogenesis of Down syndrome

A
  • 3 copies of chromosome 21
  • Failure of separation of chromosmes (during meiosis I of gametogenesis) - this is called nondisjunction (94%)
  • translocation of the long arm of chromosome 21 to another chromosome such as 14 accounts for 5% of cases
  • Mosaicism - failure of chromosome separation during MITOSIS
12
Q
A