Week 3 Down Syndrome Describe the clinical features of Down Syndrome

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Week 3
Down Syndrome
1. Describe the clinical features of Down Syndrome
• In regards to the clinical features of down syndrome, one must look at both physical and cognitive characteristics.
Common Physical features


Abnormally small chin

Mongoloid fold

Fold of the upper eyelid on the inner corner of the eye

Shortened limbs

Shortened hands, feet and long bones (arms and legs), neck


Curvature of the 5th fingers (little fingers) and toes towards the others


Low muscle tone

Protruding tongue

Due to small oral cavity

Brushfield spots

White spots on the iris

Single palmar creases

A single transverse palmar crease instead of the usual two


Small teeth, flattened face/nose, excessive space between large toe and second toe, flexible ligaments

• It is also common for Down Syndrome patients to suffer abnormalities to other bodily systems and organs.

  • Congenital heart disease is the most concerning problem with Down syndrome patients with many developing sever cardiovascular problems in later life (most commonly a ventricular septal defect).

  • Also get GI tract abnormalities, respiratory and endocrine issues.

Cognitive Characteristics

  • Most patients with Down Syndrome have a decreased intellectual capability, with the severity of this trait varying on a case by case basis (can range anywhere from IQ 30 – IQ 70).

Note: Individuals with mosaic Down Syndrome have IQ of 10 – 30 points higher.

  • Also a delay in motor skills and speech.

  • Nevertheless, patients with Down Syndrome are described as happy, affectionate, caring and playful people

2. Outline the epidemiology of Down Syndrome in the Australian population and in population subgroups.
• Down syndrome is the most common chromosomal condition affecting newborn babies.

• It is due to trisomy 21, which can manifest in a variety of different ways.

• It has been shown that the chance of a woman having a Down Syndrome child increases with age (see diagram below from NSW centre for genetic education)

• It was difficult to find the prevalence of Down syndrome in population subgroups in Australia. Nevertheless, I found a table in a paper from the American Journal of Epidemiology describing the prevalence of Down Syndrome in California between differing ethnic groups. (see diagram on next page)

• Although from a different country, it clearly shows that the Asian population has the highest risk of having Down Syndrome children whilst the African American population have the lowest risk.

Note: The open squares are observed live births while the coloured squares are adjusted total live births.

3. Discuss the causes of Down Syndrome and how these affect the likelihood of recurrence within families.
• There are three genetic variations that can cause Down Syndrome.

  1. Trisomy 21

  • Seen in 95% of all cases of Downs Syndrome

  • The extra copy of chromosome 21 is apparent in cells of the baby

  • It is caused by meiotic nondisjunction

  1. Mosaic Down Syndrome

  • Extremely rare and occurs in about 1% of all cases

  • Some of the cells in the baby have 47 chromosomes (trisomy 21) whilst others have the usual 46.

  • The number of cells which contain the extra chromosome 21, and in which tissues or organs they occur, effects the severity and characteristics of condition

  • It is caused by abnormal cell division shortly after fertilization

  1. Translocation Down Syndrome

  • Seen in 4% of all cases

  • Extra copy of chromosome 21 is attached (translocated) to another chromosome

  • It is an inherited form of the condition and carriers have a 2-3% chance of having a down syndrome child.

    • Robertsonian Translocation most common form of Translocation Down Syndrome.

      • Usually when 21 chromosome attaches to 14 – called a fourteen, twenty one translocation, written t(14:21)

      • Down Syndrome will occur when there are two chromosome 21, one 14, and one t(14:21)

      • From PBL it was worked out that if female has Robertsonian Translocation and mates with normal father, there are 6 possible outcomes: 3/6 chance death (due to monosomy and one due to trisomy 14), 1/6 chance completely normal, 1/6 down syndrome, 1/6 normal phenotype but abnormal genotype.

4. Describe the effects of Down Syndrome at personal and societal level, identifying community support services available.
Down Syndrome affects, but does not determine, development and achievement in a person.

• People with Down Syndrome demonstrate a wide range of capabilities.

• People with Down Syndrome usually live with family or paid staff who assist them in their daily lives

• These days Down Syndrome people can:

  • Attend childcare settings, pre-schools, primary and high schools alongside other children of their age.

  • Adults with Down Syndrome attend post-school training, participate in the workforce and are valued members of the community.

  • An increasing number are achieving independent living, with some level of support, within the community.

• A GP plays a vital role in monitoring the health and well being of both Down Syndrome patients and their family. Vigilance is required with regard to a change in behaviour or function that may indicate physical disease, sensory deterioration, medication side effects or mental health disorder.
• Also, Down Syndrome NSW is an independent charity established in 1980, and run by families. It is funded by private and public donations, and NSW health. They provide many services for people with Down Syndrome, their families, and others working with people with Down Syndrome.

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