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Down’s syndrome or trisomy 21 is a genetic condition arising due to an extra 21st chromosome. This causes a range of difficulties including learning disabilities and physical malfunctioning.

Down's syndrome is quite common, occurring in one in every 700 to 900 newborns worldwide and is essentially present since birth. Since it is a genetic condition, it is not precisely controllable or even completely reversible. Though some form of physical, intellectual and health-related disability is bound to occur, most people living with Down’s syndrome have a normal life, while others may require some assistance to reach that goal.

It is imperative that these individuals be provided with complete physical, emotional and mental support from their communities.

This article will discuss the symptoms, causes and management of Down’s syndrome, so that you can better understand the condition.

  1. What causes Down Syndrome
  2. Down’s syndrome features and symptoms
  3. Down’s syndrome screening and diagnosis
  4. Preventing Down’s Syndrome
  5. Down’s Syndrome treatment: Living with Down’s
  6. Prognosis of Down’s Syndrome: life expectancy

All the cells present in our bodies are expected to possess 46 chromosomes for their normal functioning. However, individuals with Down’s syndrome have 47 chromosomes, the extra one being chromosome 21.

Chromosomes are supercoiled DNA strands which work in pairs to perform optimally. The only cause of Down’s syndrome is this extra copy of chromosome 21 or sometimes an extra piece of it. This means that each body cell has three copies of chromosome 21, instead of two, present conventionally. This is why it is also called trisomy 21. This extra copy or piece is responsible for all the physical, intellectual and other health-related issues that the sufferer has to face.

But, it is important to note that the occurrence of trisomy is indispensably a genetic event and neither the parent nor the affected has any control over the condition. It occurs at the time of conception itself and cannot be reversed.

The chromosomal abnormality responsible for the development of this syndrome occurs as an utterly random event during the formation of gametes or reproductive cells in either of the parent. Usually, this abnormality develops in the egg cells but sometimes it can even occur in the sperm. This is when an extra chromosome 21 is formed. If these abnormal cells continue to take part in the process of fertilisation, the extra chromosome will be expressed in the zygote and will thereafter be a component of the foetal cells.

When following this mechanism, Down’s syndrome is not inheritable. This means that Down’s syndrome resulting from trisomy 21 is not caused because of an abnormality in the parents and is not passed down from them in any form.

But, there is a form of this disorder which is possibly inheritable. This is believed to be caused by the process of translocation, and it is then called translocation Down’s syndrome. Translocation occurs when a part of chromosome 21 attaches itself to another chromosome during the process of genetic formation. This could either occur in either of the parental reproductive cells, the sperm or the ova, or at the time of fertilisation. It may even occur during early stages of foetal development. This is what refers to the extra piece of chromosome 21 mentioned above. So, foetuses acquiring this extra material from chromosome 21 will have two of chromosome 21 and genetic material from this extra piece, getting it down to the same scenario of having 3 of these chromosomes.

The parent of the affected already carries this disrupted form of genetic material between chromosome 21 and the other chromosome. But, since this disruption is balanced, the parent does not exhibit any symptoms. When passed on to the offspring, an imbalance in this genetic material is likely to occur, causing this extra material from chromosome 21 to lead to the expected symptoms of Down’s syndrome.

The extra chromosome in Down's syndrome is ascertained to be present in every single cell of the body, of all the million we contain. However, sometimes, it is only represented in some or few of these cells and is then called mosaic Down’s syndrome. This implies that some of the body cells have a normal genetic composition, while others possess 47 chromosomes. Even this type cannot be inherited by the offsprings.

Heredity is not a quite common cause of Down’s syndrome with only 1% of the total cases being reported owing to inheritance. Only the types resulting from translocation of the chromosome are inheritable, which occurs in one-third of the total occurrences.

Parent giving birth to a baby affected with Down’s syndrome have a 1 in 100 chance of its occurrence in the second baby. This risk is about 10-15% from a maternal carrier and only 3% when the father is a carrier of the gene.

Down’s syndrome presents with a number of physical characteristics and intellectual disabilities along with various health-related issues. These can be ascertained to be the symptoms of the condition, which can be listed as:

Physical and functional characteristics of Down’s syndrome

Following are the physical and functional traits, which will be most commonly noted at birth or during infancy if the individual has this syndrome:

  • Being underweight at birth with a lesser than average height
  • Flat back of the head
  • Flattened facial profile with a typically flat nose
  • Slanting of the eyes due to a skin fold hanging from the upper eyelid and covering the inner corner of the eye
  • Hypotonia or floppiness: Lower muscle tone, making the head to flop due to a poor tone of neck muscles
  • A short neck with an excess skin at the back of the neck
  • Newborns, when held, may feel limp and may later develop swallowing and sucking difficulties
  • Delayed landmarks of physical development in infancy including a delay in sitting, walking and feeding, due to the effects of hypotonia
  • Small head and ears
  • Small mouth, which may cause the tongue to stick out
  • Wide short hands and a small palms along with a characteristic single crease on it
  • A deep groove between the first and second toes

While these are the physical traits of the syndrome, it is important to note that these may not be present in all. Every individual with Down’s syndrome does not appear the same, though, they certainly bear familial similarities. Similarly, they will function distinctly and have individual traits and pace of development.

It is important to not compare or generalise since they may have slower development than other children without the condition, which will also increasingly vary among children with the condition.

Intellectual functioning of individuals affected with Down’s syndrome

Children and adults with Down’s syndrome often have some form of cognitive impairment causing problems with comprehension, analysis, thinking and learning. But, this may be different among different individuals causing mild to moderate effects. Following problems may be noted:

  • A short attention span
  • Slow learning
  • Poor judgment
  • Reduced retention
  • Learning difficulties
  • Mental retardation
  • Delayed language and speech development
  • Impulsive behaviour

Over the course of time, these children develop the required communication skills with the help of parental and societal support, which helps them integrate within the community.

Associated disorders with Down’s syndrome

Individuals affected with Down’s syndrome are likely to develop a variety of other conditions due to developmental problems. These include:

  • Autism
  • Hearing loss
  • Vision disorders
  • Heart abnormalities
  • Hormonal disorders and problems with the functioning of certain glands
  • Digestive issues
  • Gastroesophageal reflux disorder, which causes the regurgitation of stomach contents into the oesophagus
  • Celiac disease (an inability to digest gluten)
  • Hypothyroidism (low levels of thyroid hormone)

Since the extra chromosome resulting in Down’s syndrome is represented in every cell of the body, individuals suffering from this condition will have a number of physical and health-related issues. While these may vary from person to person, heart abnormalities are most commonly noted among individuals with this syndrome.

Down’s syndrome is easily diagnosable at birth or during infancy due to the presence of characteristic clinical findings. For a confirmed diagnosis, a blood sample or a skin sample is examined and tested for the presence of an extra chromosome 21. This test is known as chromosome analysis.

Alternatively, the chances of Down’s syndrome can be detected during foetal life through the process of screening, which is offered to every pregnant woman. While this does not give a clear diagnosis, it ascertains the risk. Parents can then be counselled and educated about this syndrome, which will enhance their preparedness to nurture the baby.

More comprehensive tests to detect the risk include:

  • Amniocentesis: In this procedure, a sample of amniotic fluid surrounding the baby is tested between 15-20 weeks of pregnancy.
  • Chronic villus sampling: This involves testing a small sample of the placenta during 11-14 weeks of pregnancy.

No. Down’s syndrome cannot be prevented since the genetic makeup cannot be manipulated. However, some researchers say that the risk of Down’s syndrome increases as a woman ages. So, controlling this factor and planning your pregnancy earlier may help to reduce the risk, but it cannot be completely avoided.

  • Down’s syndrome can not at all be treated. There is not much that can be done to control or rectify genes. But, the quality of life of those affected can certainly be improved. Treatment of any physical or mental condition experienced by the individual can help to achieve this aim.
  • Children affected with Down’s syndrome require immediate care and attention with long-term treatment well continuing throughout the entire lifetime.
  • It has been demonstrated that early treatment programs can help to enhance skills in childhood.
  • Some children may need speech-language therapy with the help of a professional trainer in order to improve their communicative skills. In some cases, this may require the help of sign language or pictures until speech is functional.
  • Occupational therapy can also be instituted in the early stages to accomplish daily tasks and activities, like eating, brushing, holding a pen or using a computer. Since the motor skills of those affected with Down’s syndrome are compromised, this can be achieved with the help of exercises that help in improving muscle tone and movement, so that normal functions can be performed.
  • Children with learning difficulties require additional care and support. Those with Down’s can go to either a normal school or a special school depending upon their competencies and preferences. There are several programs which offer free education for these children. It is important to enrol them in a school that caters to their special needs.
  • Those born with a heart defect will need a corrective surgery and support thereafter to improve their survival and to enhance their quality of life.
  • Children with digestive issues will require to follow a special diet throughout their lives. In case of celiac disease, this will involve limiting all foods containing gluten, which includes all types of bread, roti and several other items. It is important to visit a specialist and get a specialised diet plan for this condition.
  • Antacids may also be prescribed in case the individual suffers from gastroesophageal reflux disorders.
  • So, any kind of difficulties and problems associated with the condition can be completely managed, while the syndrome remains incurable. It is important to seek medical help in case of any of these problems to manage them at the earliest. Regular medical checkups and vaccinations whenever needed are important, as they are for every child.
  • When given the right support and offered associated treatments, individuals living with Down’s syndrome have an equal potential to lead a normal and productive life. They may require behavioural therapies and counselling sessions to cope up with any interpersonal issues or mental health concerns. Hearing and assistive devices may also be needed in those with disabilities. It is important to meet all the needs of individuals with Down's.
  • Parental and societal support also goes a long way in managing psychological issues related to the condition.

With increasing medical advancement, the prognosis of Down’s syndrome has significantly improved and it is common for affected individuals to a live a normal life beyond the age of 50. However, the risk of Alzheimer’s and dementia is high among them at this age.

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References

  1. National Institutes of Health; [Internet]. U.S. Department of Health & Human Services; Down syndrome.
  2. National Down Syndrome Society. Down Syndrome. New York [Internet]
  3. National Health Service [Internet]. UK; Hypotonia.
  4. National Health Service [Internet]. UK; Down's syndrome.
  5. Eunice Kennedy Shriver National Institute of Child Health and Human; National Health Service [Internet]. UK; What are common symptoms of Down syndrome?
  6. National Human Genome Research Institute. About Down Syndrome. National Institute of Health: U.S Government
  7. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Down Syndrome
  8. Eunice Kennedy Shriver National Institute of Child Health and Human; National Health Service [Internet]. UK; What are common treatments for Down syndrome?