Originally appeared on Mayo Clinic

Definition

Down syndrome is a genetic disorder caused when abnormal cell division results in extra genetic material from chromosome 21. This genetic disorder, which varies in severity, causes lifelong intellectual disability and developmental delays, and in some people it causes health problems.

Down syndrome is the most common genetic chromosomal disorder and cause of learning disabilities in children.

Better understanding of Down syndrome and early interventions can greatly increase the quality of life for children and adults with this disorder and help them live fulfilling lives.

Symptoms

Each person with Down syndrome is an individual — intellectual and developmental problems range from mild to moderate, and some people are healthy while others have severe health problems such as serious heart defects.

Children with Down syndrome have a distinct facial appearance. Though not all children with Down syndrome have the same features, some of the more common features are:

• Flattened facial features
• Small head
• Short neck
• Protruding tongue
• Upward slanting eyes, unusual for the child’s ethnic group
• Unusually shaped or small ears
• Poor muscle tone
• Broad, short hands with a single crease in the palm
• Relatively short fingers and small hands and feet
• Excessive flexibility
• Tiny white spots on the colored part (iris) of the eye called Brushfield spots
• Short height

Infants with Down syndrome may be average size, but typically they grow slowly and remain shorter than other children the same age. In general, developmental milestones, such as sitting and crawling, occur at about twice the age of children without impairment.