What is Down's syndrome?
Down's syndrome is a genetic abnormality known as trisomy, where a person inherits an extra copy of one chromosome – in this case chromosome 21 – so there are three copies of this chromosome instead of the usual two.
First recognised in 1866 by Dr John Langdon Down (after whom the condition is named) it affects a baby's normal physical development and causes lifelong mild to moderate learning difficulties.
There are three main types of Down's syndrome;
- Regular trisomy 21; over 90% of people with Down's syndrome have this form, where all their cells have an extra chromosome 21.
- Translocation; this accounts for around 4% of cases and in this form the extra chromosome 21 material is attached to another chromosome. This means that one of the parents may have no sign of the condition themselves.
- Mosaic; here only some of the cells have an extra chromosome 21, and so people with this type of Down's syndrome often have mild features of the condition.
How common is Down's syndrome?
It is relatively uncommon, with around 1 in every 1,000 live births being affected by it.
All ethnic groups can be affected with boys being very slightly more likely to be affected than girls.
The main risk factor appears to be the age at which the mother gives birth – the older she is the higher the risk.
The risks are;
- At 20 years old – 1 in 1,500.
- At 25 years old – 1 in 1,300.
- At 30 years old – 1 in 900.
- At 35 years old – 1 in 350.
- At 40 years old – 1 in 100.
- At 45 years old – 1 in 30.
Screening for Down's syndrome in the UK is carried out during the early stages of pregnancy but is not compulsory.
This testing should ideally be done in the first trimester of pregnancy.
What are the symptoms of Down's syndrome?
People with Down's syndrome tend to have a characteristic appearance, with a flat facial profile, protruding tongue and eyes that slant slightly upwards.
They are typically shorter than average, with short broad hands that have a single crease across the palm. They have varying degrees of learning disability ranging from very mild to severe and autism occurs more commonly with them.
In general, their personality tends to be gentle, warm and cheerful. With modern advances in medicine, most Down's syndrome children can now expect to live to their 50's or older, with the first year of life being the most dangerous time medically – about 15% of Down's syndrome children die in the first 12 months of life, usually due to complications arising from congenital heart disease.
What are the treatments for Down's syndrome?
There is no cure for Down's syndrome. Treatment of accompanying health problems is available depending on the severity of the condition and includes speech therapy, physiotherapy and educational programmes.
Some can happily lead relatively normal and semi-independent lives whereas others require full-time care.
Further advice and support can be found at Down's Syndrome Association
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