Down Syndrome

Down syndrome is a common congenital chromosomal anomaly which is found worldwide. The condition occurs when there is one extra copy of chromosome 21 in cells in the body. The extra chromosome 21 material may affect the physical development and learning abilities of people with Down syndrome. Down syndrome is the most common genetic cause of learning disability. Down syndrome is not a disease or an illness that can be cured. 

down syndrome

Facts about Down Syndrome

Down syndrome was first described by Dr John Langdon Down in 1866. Down syndrome affects people of all economic, educational, cultural, ethnic and racial categories.

The chance a baby with Down syndrome increases with the age of the mother, however, 80 percent of babies with Down syndrome are born to 35 years old or younger women, simply because women in that age group have the most babies.

Down syndrome causes developmental delays and, typically, mild to moderate cognitive impairment. Both, however, range across a broad span and the degree of delay and impairment is highly individual.

Types of Down Syndrome

  • Trisomy 21, in which there is an extra copy of the 21st chromosome in all cells, is by far the most common and occurs at conception.
  • Mosaic down syndrome is relatively rare and occurs sometime after conception when some cellular division has taken place. As a result, most but not all cells have an extra 21st chromosome.
  • Translocation, in which an extra copy of the 21st chromosome adheres to another chromosome, is the rarest form and the only inherited type.


The presence of Down syndrome is often identified soon after birth from the baby’s clinical features and confirmed with a blood test. Sometimes babies with Down syndrome are identified during pregnancy as a result of prenatal tests.

Characteristics of Down Syndrome

  • The face tends to be round and flat.
  • Ears may also be small and low-set.
  • The nose may be small with a flat and low bridge.
  • The back of the head (called the occiput) is slightly flattened.
  • Eyes slant upwards and have an extra fold of skin on the upper eyelid known as an epicanthic fold or the epicanthus. This skin fold covers the inner corner of the eye next to the nose.
  • The mouth cavity is slightly smaller than average and the tongue slightly larger causing the person with Down syndrome to sometimes protrude his/her tongue.
  • With speech and language therapy from an early age, tongue protrusion can be managed through exercises that strengthen the lips and tongue.

Stay tuned with BYJU’S to learn more about the Down Syndrome.

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