21 Mar 2012

World Down syndrome day

Today is World Down Sydrome Day so I thought I would post the facts about Down Sydrome for anyone who doesn't know about it and is curious.

Also, I'm running a charity auction this week to raise money for Down's syndrome association, it's international so go check it out HERE if you haven't already, you might be able to grab yourself a bargain!

Causes of Down's syndrome

Down’s syndrome is a genetic condition that occurs as a result of an extra chromosome.

Chromosomes

Chromosomes are blocks of deoxyribonucleic acid (DNA) that are found in every cell in the human body. Chromosomes contain a detailed set of genetic instructions that control a wide range of factors, including:
•how the body’s cells develop
•the colour of a baby’s eyes
•the sex of a baby

A healthy person inherits 46 chromosomes from their parents – 23 from their mother and 23 from their father.

Chromosome 21

Down’s syndrome is caused by abnormalities that affect the twenty-first chromosome, known as chromosome 21.
Chromosome 21 can be affected in three main ways, leading to the three main sub-types of Down’s syndrome. These are explained below.

•Full trisomy 21 Down’s syndrome is the most common type of Down’s syndrome, accounting for 94% of all cases. Full trisomy 21 develops because every cell in the body has an extra copy of chromosome 21 (trisomy is a Greek word that means ‘third copy’).
•Mosaicism Down’s syndrome is the least common type of Down’s syndrome, accounting for 2.5% of all cases. In cases of mosaicism Down’s syndrome, some but not all cells have an extra copy of chromosome 21. The symptoms of mosaicism Down’s syndrome tend to be milder and less wide ranging compared with the other types.
•Translocation Down’s syndrome - is caused when a piece of chromosome 21 attaches itself to another chromosome in a cell. It accounts for 3.5% of cases of Down’s syndrome. The symptoms of translocation Down’s syndrome are similar to those of full trisomy 21 Down's syndrome but, unlike this form of the condition, it is occasionally possible for a parent to pass translocation Down’s syndrome on to their child.

It is thought that some people do not have symptoms of translocation Down’s syndrome but they have altered genetic material that can trigger the condition in their children. These people are known as translocation carriers.
The risk of a translocation carrier passing on the condition to their child depends on their sex (this is due to the way that chromosomes are passed down through families). That is:
•male carriers have around a 1 in 35 chance of passing on the condition
•female carriers have around a 1 in 8 chance of passing on the condition

However, it is thought that most cases of translocation Down’s syndrome are not inherited in this way.
Effects of chromosome 21

The extra copy of chromosome 21 in children with Down’s syndrome leads to many parts of their body not developing properly.
Chromosome 21 is the smallest of all the chromosomes, but it still contains more than 300 different genes (units of genetic material). It is thought that many of the genes play an important role in the development of key functions of the body, including:
•the development of the heart
•the development of the brain
•the development and regulation of the metabolism (the rate at which the body uses energy)

Risk factors

It is not fully understood why some babies are conceived with abnormal copies of chromosomes. However, there a number of risk factors which are thought to increase the risk of having a baby with Down’s syndrome.

Maternal age

The maternal age (the age of a woman when she becomes pregnant) is the only clear risk factor to be identified as increasing the risk of having a baby with Down’s syndrome.
The risks of having a pregnancy that is affected by Down’s syndrome increases as a woman gets older. For example, a woman who is:
•15-29 years of age has a risk of 1 in 1,500
•30-34 years of age has a risk of 1 in 800
•35-39 years of age has a risk of 1 in 385
•40-44 years of age has a risk of 1 in 106
•45 years of age has a risk of 1 in 30

However, approximately 80% of babies with Down's syndrome are born to mothers who are under 35 years of age. This is due to the fact that women under 35 make up the majority of the child-bearing population.

Environmental factors

There is some evidence to suggest that ‘clustering’ of new cases of Down’s syndrome does occur. Clustering means that an above-average number of cases develop over a short to medium period of time in one specific geographical area, such as the district of a city, or in a village.
This clustering of Down’s syndrome cases could be the result of chance, but some researchers have suggested that there may be certain environmental factors that increase the risk of the condition. Such factors include:
•exposure to infectious agents, such as viruses, during pregnancy
•using oral contraception
•smoking during pregnancy
•exposure to radiation
•exposure to pesticides
•living near waste-disposal facilities, such as landfill sites or waste incinerators

There is little in the way of hard evidence to support any of the suggestions listed above. However, smoking is known to increase the risk of stillbirth, miscarriage and premature birth.

Further research is required in order to confirm or disprove whether environmental factors play a role in Down’s syndrome
What is Down's Sydrome?
 
Down’s syndrome is a genetic disorder that was named after John Langdon Down, the doctor who first recognised it as a distinct condition in 1866.

Down’s syndrome affects a baby's normal physical development and causes mild to moderate learning difficulties. It is a lifelong condition that develops when a baby is still in the womb (uterus).
Children who are born with Down’s syndrome also have a higher chance of developing other conditions, some of which are life-threatening. For example:
•congenital heart disease – a general term that describes a series of birth defects that affect the heart
•sight and hearing problems
•Alzheimer’s disease – a common form of dementia (a deterioration of mental abilities, such as memory and reasoning) that often affects people who are over 65 years of age

How common is Down’s syndrome?

Down’s syndrome is uncommon in the UK. For example, from 2007 to 2008, 1,843 cases of Down’s syndrome were diagnosed during pregnancy, and 743 babies were born with the condition. This means that about 1 in every 1,000 live births is affected by Down’s syndrome.
Down’s syndrome affects all ethnic groups equally. Boys are slightly more likely (around 15%) to be born with Down’s syndrome than girls.
The cause or causes of Down’s syndrome are unclear, but the single biggest risk factor for the condition seems to be the age at which a woman gives birth. The older a woman is when she has a baby, the higher the risk of her baby having Down’s syndrome. The greatest risk (1 in 30) is associated with women who are 45 years of age or over.
Screening

Routine screening for Down’s syndrome is carried out during pregnancy in order to identify women who are at high risk of giving birth to a child with Down’s syndrome.

If screening proves positive (confirms that the baby has Down’s syndrome), counselling is available to provide support and information, so that the woman and her partner can make an informed decision about whether to proceed with the pregnancy.
Outlook

The outlook for Down’s syndrome can vary widely, depending on whether a child with the condition also develops any other serious health conditions.
Children with Down’s syndrome are most vulnerable during the first year of their life. About 15% of children with Down’s syndrome will die during the first year, usually from a complication that arises from congenital heart disease.
After the first year of life, the outlook for children with Down’s syndrome improves dramatically. Due to advances in treatment, the average life expectancy for a person with Down’s syndrome is around 50, and this may well improve in the future.
Every child’s personality is different, and it is important never to stereotype a person with Down’s syndrome. However, in general terms, people with Down’s syndrome tend to have warm, gentle and cheerful personalities, despite the day-to-day problems they have to face.

Symptoms of Down's syndrome


The symptoms of Down’s syndrome can affect a person in many different ways. However, the most obvious symptom of the condition is its effect on a person’s physical appearance.

Physical appearance

People with Down’s syndrome tend to have a number of typical physical features. Some people with the syndrome only have a few of these features, while others are more severely affected.

The physical features of Down’s syndrome may include:
•eyes that slant upwards
•small ears
•flat back of head
•small mouth
•protruding tongue
•flattened nose bridge
•white spots on the iris (the coloured part of the eye), known as Brushfield spots
•short fingers
•broad hands with a single crease across the palm
•loose skin on the back of the neck
•loose joints (babies in particular may seem ‘floppy’)
•poor muscle tone (hypotonia)
•low birth weight
•vertical skin folds (epicanthic folds) between the upper eyelids and inner corner of the eye

Learning difficulties

All children with Down’s syndrome will have learning difficulties, which can range from mild to moderate.
One way of measuring a person’s intelligence is to use a type of test called an intelligence quotient (IQ). An IQ test involves exercises that are designed to assess specific capabilities.
The average IQ score for the general population is 100. People with Down’s syndrome have an IQ of 25 to 80, with an average score of 50.

In particular, children with Down’s syndrome may have:
•memory problems – both short-term and long-term memory
•concentration problems – many children have low attention spans
•difficulty problem solving
•difficulty understanding the consequences of their actions

Delayed development

Children with Down’s syndrome have delayed physical and mental development.
Children with Down’s syndrome are usually much shorter than other children their age. Growth continues through childhood but most adults with Down’s syndrome are below average height – around 158cm (5.2ft) for men and 140cm (4.6ft) for women.

With regards to mental development, children with Down’s syndrome usually take longer to reach important developmental milestones, such as:
•learning to crawl
•learning to walk
•learning to speak
•learning to read
•learning the social skills that are used for social interaction

It is important to recognise that a child with Down’s syndrome may still be able to acquire most, if not all, of the mental and social skills that most other people develop. Their development simply occurs at a slower pace.

All information was sourced from NHS.

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