Alton Street Surgery Patient Information Leaflet
Down’s Syndrome
What is Down's syndrome?
The word syndrome means a collection of signs or characteristics. The name
Down comes from the doctor, John Langdon Down, who first described the condition
in 1866. There are more differences between people with Down's syndrome than
there are similarities. They will have many of their families' distinctive
characteristics and will therefore resemble their brothers and sisters.
As well as these individual characteristics however, they will have physical
features shared by others with Down's syndrome. They will also have learning
disabilities. This means they have greater difficulty learning than the
majority of people of the same age.
About one in one thousand babies born in Britain will have Down's syndrome.
Characteristics
Down's syndrome is normally suspected soon after birth because a doctor, nurse
or sometimes a parent recognises the characteristic features. Chromosome tests
are then carried out to confirm the diagnosis.
The features which people look for include:
·
Eyes that slant slightly
upwards and outwards. They often have a fold of skin that runs vertically
between the two lids at the inner corner of the eye (the epicanthic fold).
·
A head which is rather flat
at the back with a hairline that is low and ill-defined at the nape of the
neck, often with rather loose skin in this area.
·
A face that appears
somewhat flat.
·
A mouth cavity that is
slightly smaller than average, and a tongue that is slightly larger.
·
Hands that are broad, with
short fingers, and a little finger that curves inwards. The palm may have only
one crease across it.
·
A deep cleft between the
first and second toe extending as a long crease on the side of the foot.
·
Reduced muscle tone which
results in floppiness (hypotonia). This improves spontaneously as the child
gets older.
·
A below average weight and
length at birth
Most of these characteristics
may be found in children who do not have Down's syndrome. It is the combination
of several or all of these which would alert medical professionals to the
possibility that a baby might have the condition.
Once a diagnosis of Down's syndrome has been confirmed by a chromosome test, genetic counselling should be available to the family.
Genetics
Down's syndrome or Trisomy 21 (tri = three, soma = body) is a genetic condition
caused by the presence of an extra number 21 chromosome. Normally there are
46 chromosomes in every human cell (apart from eggs and sperm, which have
23). Half of these come from our mother and half from our father. The person
with Down's syndrome has an extra chromosome 21, making 47 in all. This results
in a disruption to the growth of the developing baby.
This extra chromosome can come from either the mother or the father, and is
present because of a genetic accident when the egg or the sperm is made, or
during the initial cell division following conception.
Regular Trisomy 21
There are three different types of Down's syndrome. 95% of people with Down's
syndrome have the type known as Standard or Regular Trisomy 21. When a person
has this kind of Down's syndrome, every cell has the extra number 21 chromosome.
This type of Down's syndrome is always an accident of nature, i.e. it is not
hereditary. It can happen to anyone and there is no known reason why it occurs.
Translocation
Some 4% of people with Down's syndrome do not have an extra whole, separate
chromosome 21, but have an additional part of chromosome 21 attached to another
chromosome. This usually arises when the small arms of chromosome 21 and another
chromosome break, and the two remaining long arms join together at their exposed
ends. This process is called translocation (because the chromosome material
has transferred its location). In two-thirds of people with Down's syndrome
due to a translocation, the translocation was an isolated event during the
formation of the individual egg or sperm involved in their conception. As
with regular trisomy 21, there is no known reason why this occurs. It cannot
be predicted and it is not a result of anything the parents or other family
members have done.
The other one-third of people with a translocation will have inherited it
from one of their parents. This parent has two whole number 21 chromosomes
in each cell but one of them is attached to another chromosome.
Mosaicism
People with mosaic Down's syndrome have an extra chromosome 21 in only some
of their cells. They therefore have a mixture of trisomic cells and ordinary
cells. The mixture can vary from very few to nearly 100% trisomic cells. Depending
on the proportion of trisomic cells, and which parts of the body contain these
cells, individuals may be less affected both in their physical features and
in their ability level than those with regular trisomy or translocation.
In all types of Down's syndrome, it is not possible to say at birth how affected
a person will be, only time will tell as the child develops. In the vast majority
of cases of Down's syndrome the condition is NOT HEREDITARY.
Health
Many people with Down's syndrome enjoy a healthy life, and a life span of
40-60 years in now not unusual.
Certain medical conditions are more common in people with Down's syndrome,
for example:
·
About 40% have heart
problems at birth, half of which are serious and require surgery and/or
medication. An echocardiogram should be carried out on all new babies with
Down's syndrome.
·
More than half of children
with Down's syndrome have significant hearing problems and problems with vision
are more common. Regular monitoring of these should be carried out throughout a
person's life.
·
It is likely that up to 30%
of people with Down's syndrome may develop thyroid disease. This should be
monitored regularly and can be treated with the appropriate medication.
·
More minor complaints such as
dry skin and frequent and persistent coughs and colds are also more common.
It is not inevitable that
people with Down's syndrome are unwell, they can be very well, and the right to
be so should not be influenced by the fact that they have Down's syndrome.
The Future for People with Down's syndrome
There is no cure for Down's
syndrome, however, programmes do exist to help children with Down's syndrome to
achieve their full potential. In most areas, Child Development Centres exist to
give parents access to speech therapy, physiotherapy, and early intervention
schemes such as Portage, all of which can help the development of children with
special needs. Your Health Visitor should be able to tell you what is available
in your area.
The majority of children with Down's syndrome will learn to walk, run, climb,
ride a bike, speak, feed themselves etc. like other children. Usually, it will
usually take them longer to learn these skills than other children. Many
children are able to attend their local school with support and become well
integrated into the community. Nowadays, it is not unusual for young adults
with Down's syndrome to have jobs.
Prenatal Screening and Testing for Down's syndrome
Most NHS Trusts in Britain now
offer pregnant women screening tests for Down's syndrome. Screening tests can
be blood tests, such as the AFP test, Double, Triple, Triple plus, nuchal
translucency scan or a combination of blood test and scan. Such tests can only
give an indication as to whether a woman has a higher chance than other women
of the same age of carrying a baby with Down's syndrome. If you are found to
have a higher chance than 1:250, your result will be termed 'screen positive';
this does not mean your baby definitely has Down's syndrome. The majority of women
with 'screen positive' results will not go on to have a baby with Downs'
syndrome. A 'screen negative' result, i.e., one which gives a lower chance of
the baby having Down's syndrome does not mean that your baby definitely does
not have Down's syndrome. The chance of having a baby with Down's syndrome does
increase with the age of the mother, but every woman has a chance of having a
baby with the condition. No screening or diagnostic test can predict the level
of ability or disability of the child.
If, according to a screening test, you have a higher chance of having a baby
with Down's syndrome, you will probably be offered an invasive diagnostic test
such as amniocentesis to find out definitely whether the baby has Down's
syndrome. Amniocentesis does carry a risk of miscarriage of 1%. If the
amniocentesis shows that your baby does have Down's syndrome, you will be
offered the option of terminating the pregnancy. Ideally, women should be
offered counselling alongside the screening and testing programme so that they
can make informed decisions about their options.
Useful sources of information
Down's Syndrome Association, 155 Mitcham Road, London SW17 9PG, Tel: 0208
682 4001. For information on all aspects of the condition, including pre-natal
screening and testing.
Mencap, 123 Golden Lane, London EC1Y 0RT, Tel: 0207 454 0454.
Support Around Termination for Fetal Abnormality (SATFA), 73 Charlotte Street,
London W1P 1LB, Tel: 0207 631 0285.
This patient information
leaflet has been adapted from an original published by Clinnix Pro, Synigence
PLC that was produced by the Down's Syndrome Association.