Down syndrome (DS) or Down’s syndrome, also known as Trisomy 21, is a genetic caused by the presence of all or part of a third copy of chromosome. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8- or 9-year-old child, but this varies widely.
Down syndrome can be identified during pregnancy by screening followed by diagnostic testing, or after birth by direct observation and genetic testing. Since the introduction of screening, pregnancies with the diagnosis are often terminated. Regular screening for health problems common in Down syndrome is recommended throughout the person’s life.
Most people have 23 pairs of chromosomes, for a total of 46. But a baby with Down syndrome has an extra chromosome (47 instead of 46) or one chromosome has an extra part. This extra genetic material causes problems with the way their bodies develop.
Signs of Down syndrome
Children with Down syndrome are often identified at birth as a result of the physical characteristics associated with the syndrome. Some children exhibit only a few characteristics; others exhibit many. Because some of these features are also seen in people without Down syndrome, genetic testing must be done to confirm the diagnosis.
The most common features associated with Down syndrome include:
- Low muscle tone (babies appear “floppy”)
- Flat facial features, with a small nose
- Upward slant to the eyes
- Small skin folds on the inner corner of the eyes
- Small, abnormally shaped ears
- Single deep crease across the center of the palm
- Hyper flexibility (excessive ability to extend joints)
- Fifth finger has only one flexion furrow instead of two
- Extra space between the big toe and the second toe
- Enlarged tonguethat tends to stick out
They also typically have poor immune function and generally reach developmental milestones at a later age. They have an increased risk of a number of other health problems, including congenital heart disease.