Down syndrome is a genetic condition that results in some level of learning disability and a characteristic range of physical features. Down syndrome is one of the most common causes of a learning disability.
In 1866 an English doctor, John Langdon Down, recognised and described a consistent pattern of characteristics among a group of people. The syndrome was named after him because he discovered it and it is now called Down syndrome or Down’s syndrome.
Learning disability significantly affects a child’s ability to learn compared with other children of their age but it does not mean a child cannot learn at all.
What causes Down Syndrome?
The human body is made up of cells. Each cell is like a factory which has everything needed for growth and to maintain the body. Every cell contain a nucleus in which genes are stored and these genes are grouped in thread-like structures called chromosomes. Usually, the nucleus of each cell contains 23 pairs of chromosomes, half inherited from the mother and half from the father, making 46 chromosomes in all.
In people with Down syndrome, all or some of the cells in their bodies contain 47 chromosomes, as there is an extra copy of chromosome 21. This additional genetic material results in the range of physical and developmental characteristics associated with Down syndrome.
Three types of genetic variation are relevant:
Trisonomy 21 – in which all the cells of the body have an extra chromosome 21. About 94% of people with Down Syndrome have this type.
Translocation – in which extra chromosome 21 material is attached to another chromosome. Around 4% of people with Down Syndrome have this type.
Mosaic – in which only some of the cells have extra chromosome 21 material. About 2% of people with Down Syndrome have this type.
The type of genetic variation that children experience does not significantly alter the effect of Down syndrome. However, individuals with mosaic Down syndrome appear to experience less delay with some aspects of their development.
Down Syndrome affects people in all races, religions and economic backgrounds and in all countries around the world. It can happen to anyone. Although the chance of having a baby with Down Syndrome increases with the mothers age, babies with the syndrome are born to mothers of all ages. Over half of children born with Down syndrome are born to mothers under the age of 35 years.
As yet, no one knows what causes the presence of the extra chromosome 21. It can come from the mother or the father. There is no way of predicting whether a person is more or less likely to make an egg or sperm with an extra chromosome.
What we do know is that no one is to blame. As far as we know, nothing done before or during pregnancy causes the syndrome.
Diagnosis and Characteristics
In some cases, babies born with Down syndrome are identified before birth as a result of pre-natal tests (either amniocentesis or chronic villus sampling). In most cases, however, the presence of the syndrome is indicated soon after birth because of the way baby looks.
A range of physical characteristics indicate that a baby may have Down syndrome.
- ‘Floppiness’ – due to reduced muscle tone (hypotonia)
- Facial features – like a flat facial profile and nasal bridge, a small nose, eyes that slant upwards and outwards and a small mouth cavity which makes the tongue appear large
- A big space between the first and second toe (sandal gap)
- A single crease across the palm (palmar crease)
- Below average weight and length at birth
- A significant number of babies will have congenital heart conditions that may or may not require surgery.
However, many of these features appear naturally in the general population and not all babies with the syndrome show all of these characteristics.
The only way to make a definite diagnosis of Down syndrome is to analyse the chromosomes in a sample of the baby’s blood. The resulting picture of the baby’s chromosomes is called a karyotype, and it shows the presence of an extra copy of chromosome 21 if the baby has the syndrome.
There is no ‘treatment’ or ‘cure’ to reverse the effects of the extra genetic material that causes Down syndrome. However, research over the last 20 years has taught us a great deal about how the syndrome affects individuals and how to promote development.
What effect does Down Syndrome have?
Some of the needs children with Down syndrome have are exactly the same as other children, but there are other things that are different.
A child with Down syndrome has the same need for love, security and stimulation as any other child. It helps if they are included in as many everyday family, learning and social experiences as possible. It is important to understand that you can positively influence a child’s development simply by providing loving care and fun.
Children with Down syndrome are all individuals. The only thing they all have in common is that they have extra chromosome 21 genes. The effect that this extra genetic material has on each child’s health and development varies a lot. Everyone will have additional needs, but each person with Down syndrome is unique and will be affected in different ways.
Children with Down syndrome share some common physical characteristics but they do not all look the same. Children will look more like their parents and siblings than other children with the syndrome. Each child’s personality is also unique. They may be sociable or shy, calm, anxious, easy to manage or stubborn – just like other children!
Children with Down syndrome also vary significantly in the progress they make with reaching, sitting, standing, walking, communicating, talking and learning to read. Some children have a greater degree of disability, complex health issues and more needs than others.
The following all help children achieve as much as possible:
- Effective healthcare
- Good parenting skills
- An ordinary family life
- Early intervention to support development
- Good education
Early intervention in this context usually means taking positive action in the first years of life. It’s impossible to predict outcomes for any individual child when they are very young but it’s important to understand that, in general, children and young people with Down syndrome are achieving much more than they did 25 years ago.
Some of the reasons for this are:
- Increased acceptance and inclusion by society
- Advances in medical care
- Better understanding of the developmental and educational needs of individuals with Down syndrome
- Better quality education