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Down’s Syndrome

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Down’s syndrome is a genetic disorder that causes mild to moderate mental retardation. Dr. John Longdon Down was the first physician in 1886 to identify this syndrome. Thus, the name Down’s Syndrome.It can affect children from all races and economic groups. It can occur is about 1 child in 830 children.

What is Down’s Syndrome?

Down’s syndrome is a genetic disorder that occurs during conception. An extra copy of chromosome 21, called as ‘Trisomy 21’ can cause a type of disorder called Down’s syndrome. The extra copy causes problems with protein production leading to a variety of birth defects. It can lead to different effects in different people. Some may suffer from changes in their physical appearance, some suffer from delayed development, behavioral problems and few develop serious health problems. No one can predict how a child with Down’s syndrome will develop.

What Causes Down’s Syndrome?

Every cell in our body has a nucleus. It's here all the genetic information, that is genes are stored. These genes carry all the information related to our inherited traits. Genes are placed in groups that appear rod-like structures. These groups are called as chromosomes. Each nucleus contains 23 pairs of chromosomes, inherited from each parent. When there is a presence of full or partial extra copy of chromosome 21, it can lead to Down’s syndrome.

This extra genetic information causes the affected person to suffer from low muscle tone, upward slanting eye shape, low muscle tone, etc. Remember, each individual may develop varying degrees of traits.

How Does Down’s Syndrome Develop?

Till now, you must have understood that  an extra pair of chromosome is responsible for Down’s syndrome. This happens due to non-disjunction. When a pair of chromosome fails to separate during formation of an egg or sperm, it is called as nondisjunction. During conception, when this egg or sperm cell forms an embryo, it leads presence of 3 copies of chromosome 21. In normal conditions, there are 2 copies of chromosome. The extra copy of chromosome is duplicated in every cell of the body. This extra copy leads to changes in the normal development of the body and brain.

The exact cause of nondisjunction is unknown. It is seen that its frequency increases in older women giving birth. The extra copy can come from either mother or father.

Is Down’s Syndrome a Heredity Trait?

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Down’s syndrome is a genetic condition. But it has been found only 1% of the cases are passed from parent to child through genes, that is heredity trait. Only in one third of the cases, it has been found one of the parents is a carrier of the traslocated chromosome.

What are the Types of Down’s Syndrome?

There are three types of Down’s syndrome. These are:

Nondisjunction (Trisomy 21)

The error in cell division called as ‘nondisjunction’ leads to Down’s syndrome. During conception one pair of 21st chromosome fails to separate in the sperm or egg. This causes each cell to develop an extra chromosome. This type is seen over 95% cases of Down’s syndrome, called as trisomy 21.


When nondisjunction of chromosome 21 occurs in of the cells, it is called as mosaicism. This causes presence of two types of cells in the body. Some contain 46 chromosomes, and some have 47 chromosomes. People with mosaicism show fewer traits of Down syndrome. This type is seen in about 1% of the cases.


In translocation of part of chromosome 21 breaks off during cell division. This part attaches itself to chromosome 14. Although, the number of chromosomes remains as 21, the extra part in chromosome 14 causes the person to develop characteristics of Down’s syndrome.

What Are the Symptoms of Down’s Syndrome?

The physical symptoms of Down’s syndrome are very distinct. These include:

  • Flat face
  • Small and broad nose
  • Large tongue
  • Upward slanting eyes
  • Abnormally shaped ears
  • Small skin folds in the corner of  eyes
  • Poor muscle tone
  • Short fingers
  • Flexible body
  • Broad hands
  • Single deep crease in the palm

Other symptoms are related to growth and development. These include:

  • Moderate to severe mental retardation
  • Develop milestones slowly than other children
  • Learn to walk late
  • Unable to take care of themselves
  • Remain shorter than other children

These children suffer from many medical problems. They develop:

  • Leukemia
  • Heart defects
  • Gastrointestinal tract obstruction
  • Hypothyroidism
  • Eye abnormalities
  • Respiratory troubles

Diagnosis of Down’s Syndrome

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Antenatal screening helps in detecting the likelihood of the baby begin born with Down’s syndrome. Thus, every pregnant lady should undergo an ultrasound test in the first trimester. It helps in detecting any structural abnormalities such as absence of fetal nasal bone. This abnormality is associated with the presence of Down’s syndrome in the fetus. The ultrasound imaging also helps detect increased fetal nuchal translucency (NT). This is an indicator for Down’s syndrome. But this alone cannot be used as a sole indicator for Down’s syndrome. It can only be determined with the help of combined test.

Other tests include a blood test that helps predict the risk of Down’s syndrome. These tests include α-fetoprotein, β-hCG, inhibin-A, unconjugated estriol and PAPP-A.

These screening tests help prepare parents for a baby that may have chances of Down’s syndrome. It also helps in making a decision for termination of pregnancy.

In most cases, parents are unaware about the baby having Down’s syndrome. It is only after birth, that one comes to know about the condition. The physical characteristics of the baby along with a blood test called a chromosomal karyotype helps in confirming Down’s syndrome.

Management of Down’s Syndrome

The best way to manage and improve the quality of life for a child with Down’s syndrome is early intervention. There are many specialized intervention programs today that help stimulate the sensory, motor and cognitive abilities in these children. There is a team of specialist like cardiologists, gastroenterologist, audiologist, endocrinologist, physical therapist, neurologists, occupational therapist, speech pathologist, etc. that help the child overcome problems and provide for his particular needs.

These children may meet their developmental milestones longer than other children without Down’s syndrome. But never give up one these children. Each child is unique. In his/her own way they will overcome the obstacles and face the challenges head on. Family support, love and care will improve the child’s quality of life. Every parent must remember, the child despite his/her limitations has succeeded in achieving certain milestones of their life. Patience and care will only help them succeed farther and live their life as independently as possible for them. Speak to your child’s doctor, therapist or counselors for further information and support that you may need in bringing up these beautiful children with Down’s syndrome.

Written by: Saptakee sengupta
Date last updated: March 13, 2015