Down's Syndrome

Down syndrome (DS) or Down's syndrome is also known as trisomy 21. It is a genetic disorder caused by the presence of extra chromosome 21 .It is typically associated with a delay in cognitive ability (mental retardation or MR) and physical growth and a particular set of facial characteristics.
The average IQ of young adults with Down syndrome is around 50 whereas young adults without the condition typically have an IQ of 100.



People with Down syndrome share a number of physical characteristics. Not everyone suffering from the syndrome will have all of them but they may include:

  • Decreased muscle tone resulting in floppiness (hypotonia)
  • Small nose and flat nasal bridge
  • Small head, ears and mouth
  • Eyes slant upwards and outwards
  • Groove between the first and second toe (sandal gap)
  • Broad hands with short fingers
  • Palm may have only one crease (palmar crease)
  • Below average weight and length at birth


Down syndrome is a genetic condition that occurs as a result of an extra chromosome (chromosome 21). Usually, cells contain 46 chromosomes. 23 are inherited from the mother and 23 from the father. People with Down syndrome, may contain 47 chromosomes as there is an extra copy of chromosome 21. The additional genetic material causes physical and developmental characteristics associated with Down syndrome. There are three forms of Down syndrome, although the effects of each type are usually similar.

  • Trisomy 21 is the most common type. Trisomy 21 is generally seen due to every cell in the body has an extra copy of chromosome 21 (trisomy is a Greek word that means ‘third copy’).
  • Translocation is caused when a piece of chromosome 21 attaches itself to another chromosome in a cell. 
  • Mosaicism is the least common type. Here, only some of the cells have an extra copy of chromosome 21. People with mosaic Down syndrome may experience less delay with some aspects of their development.



Antenatal/ Pre natal screening: Pregnant women of any age should be offered screening for genetic conditions such as Down syndrome. Antenatal screening is a way of assessing the likelihood of baby developing or already having developed an abnormality during pregnancy. The screening test used for Down syndrome is known as the ‘combined test’. It includes a blood test and ultrasound scan.

A sample of blood is taken and tested to check the levels of certain proteins and hormones. If blood contains abnormal levels of these substances then there may be an increased chance of having a baby with Down syndrome.

A special type of ultrasound scan known as nuchal translucency that measures the pocket of fluid behind the baby’s neck. Babies with Down syndrome usually have more fluid in their neck than normal. Measuring the thickness of fluid will help determine whether baby is likely to have Down syndrome.

Post natal diagnosis: Clinical examination by a paediatrician can often confirm or refute this suspicion with confidence. Systems of diagnostic criteria for such an examination include Fried's diagnostic index which includes the following 8 signs:

  • Flat face
  • Ear dysplasia
  • Tongue protrusion
  • Corners of mouth turned down
  • Hypotonia
  • Neck skin excess
  • Epicanthic fold
  • A gap between 1st and 2nd toes.

With 0 to 2 of these characteristics, the newborn can likely be said to not have Down syndrome (with less than one in 100 false negatives), with 3 to 5 of these characteristics, the situation is unclear (and genetic testing is recommended) and with 6 to 8 characteristics, the newborn can confidently be said to have Down syndrome (with less than one in 100.000 false positives).

*NHP provides indicative information for better understanding of health. For any diagnosis/ treatment purpose please consult your physician. 


There is no cure for the down's syndrome yet but there is much that can be done to help someone with the condition to lead a healthy, active and more independent life. Management strategies such as:

Early childhood intervention: Early intervention is a system of coordinated services that promotes the child's growth and development and supports families during the critical early years like Early communication intervention promote linguistic skills.

  1. Screening for common problems.
  2. Medical treatment when required
  3. A conducive family environment
  4. Vocational training that can improve the overall development of children with Down syndrome.
  5. Education and proper care will improve quality of life significantly

Plastic surgery: Plastic surgery has sometimes proved to promote and performed on children with Down syndrome based on the assumption that surgery can reduce the facial features associated with Down syndrome, therefore, decreasing social stigma and leading to a better quality of life.

Cognitive development: Individuals with Down syndrome differ considerably in their language and communication skills. It is routine to screen for middle ear problems and hearing loss, low gain hearing aids or other amplification devices can be useful for language learning.

Music therapy is useful in some patients for social and motor development.

*NHP provides indicative information for better understanding of health. For any diagnosis/ treatment purpose please consult your physician. 


Complications of Down syndrome include:

  • Heart disorders
  • Bowel abnormalities
  • Digestive problems
  • Hearing and vision impairments
  • Thyroid dysfunctions
  • Increased risk of infections
  • Blood disorders
  • Increased risk of dementia


  • LAST UPDATED ON : Oct 29, 2015
The content on this page has been supervised by the Nodal Officer, Project Director and Assistant Director (Medical) of Centre for Health Informatics. Relevant references are cited on each page.