down's syndrome head pic

Down's syndrome

Down’s Syndrome is the most common genetic cause of learning disabilities but it is not often discussed in the public sphere and you may not have had much contact with any individuals who have it. This is a genetic disorder which means that it is caused by abnormalities in your DNA (the building blocks of what makes you, you) and the severity of the condition will vary among individuals. In general you can recognize someone with Downs as it results in some distinct facial features, learning difficulties and developmental delays.

+   Symptoms

One of the most obvious symptoms of Down’s syndrome are their distinct facial features . It is important to remember everybody is unique and individuals with Down’s syndrome will all differ in the extent that they can display a number of common features

  • Flattened facial features
  • Small head
  • Short neck
  • Protruding tongue
  • Upward slanting eyes
  • Unusually shaped ears
  • Broad short hands with one deep crease across the palm
  • Short fingers

It is also common for those with Down’s syndrome to have

  • Poor muscle tone
  • Excessive flexibility
  • Learning disabilities and mild to moderate retardation
  • Developmental delays
    • Down’s Syndrome children will usually crawl, walk and talk but it will often take them twice the time of a non-Down’s Syndrome child to do so

+   Causes

Down’s Syndrome is a genetic condition that is caused by abnormalities in DNA. In the case of Down’s syndrome the abnormality will always have something to do with Chromosome 21. Human cells normally contain 23 pairs of chromosomes – this is where your DNA hangs out. You get one chromosome in each pair from your dad and one chromosome in each pair from your mum. In individuals with Down’s syndrome they will have extra genetic material. There are three different types of Down’s syndrome:

  • Trisomy 21
    • 90% of individuals with Down’s syndrome have this type of abnormality
    • They will have 3 copies of Chromosome 21 rather than the normal 2
    • This usually is due to abnormal cell division during the development of the sperm or egg
  • Mosaic
    • This is a rare form of Down’s syndrome causing just 1% of cases
    • They will have some cells that have the normal 2 copies of Chromosome 21 and some cells that have 3 copies of Chromosome 21
    • This is usually due to abnormal cell division after the egg has been fertilized
  • Translocation
    • This is also a fairly rare form of Down’s syndrome causing 4% of cases
    • Part of the Chromosome 21 becomes attached to another chromosome before conception
    • They will have the normal 2 copies of Chromosome 21 but will have extra genetic on the other chromosome
    • This is the only type of Down’s syndrome that can be hereditary and hereditary translocation causes 1% of cases
      • A parent may be a carrier of this trait without showing any symptoms. Their DNA may be rearranged but balanced and without excess genetic material

+   Risk factors

Less than 5% of children are born with Down’s syndrome. There is no way to prevent Down’s syndrome but there are a number of risks factors that are important to understand.

  • Maternal Age
    • A woman’s chance of giving birth to a child with Down’s syndrome increases as her age increases
    • At 35 year old  woman has a 1 in 350 chance of giving birth to a child with Down’s Syndrome and at 45 year old woman has a 1 in 35 chance of giving birth to a child with Down’s Syndrome
    • More woman under 35 give birth to babies with Down syndrome than those over 35 but this is due to the fact that woman under 35 have more babies than those over 35
  • Having one child with Down’s Syndrome means there’s 1% chance of having another child with Down’s Syndrome
  • Carriers of genetic translocation for Down’s Syndrome
    • Men who are carriers have 3% chance of having a child with Down’s Syndrome
    • Women who are carriers have 10-15% chance of having a child with Down’s Syndrome

+   Screening

Screening for Down’s Syndrome may be done as part of routine prenatal care depending on the mother’s age. The testing usually involves an ultra sound and blood tests to determine the risk of the child having Down’s Syndrome; if the risk is high further tests may be done to determine if the child has Down’s Syndrome. Finding out before the child is born can give the parents time to prepare for life with a Down’s Syndrome child.

+   Complications

There are a number of serious complications associated with Down’s syndrome and individuals with the condition are at a higher risk of illness

  • 50% of individuals with Down’s syndrome are born with some kind of heart defect that
    • Can be life threatening
    • May require surgery
  • Leukemia
    • Young children with Down’s syndrome are more likely to develop leukemia
  • Infectious diseases
    • Abnormalities in their immune system makes individuals with Down’s syndrome more likely to get ill with infections and conditions like pneumonia
  • Sleep apnoea
    • This is on account of  muscle and skeletal structure changes - that Down’s syndrome individuals often display – and can result in obstructing their airway
  • Dementia
    • A higher risk of dementia at a younger age (40)
  • Premature aging
  • Seizures

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