Down syndrome Health Article

Definition

Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46.

Alternative Names

Trisomy 21

Causes, incidence, and risk factors

In most cases, Down syndrome occurs when there is an extra copy of chromosome 21. This form of Down syndrome is called Trisomy 21. The extra chromosome causes problems with the way the body and brain develop.

Down syndrome is the most common single cause of human birth defects.

Symptoms

Down syndrome symptoms vary from person to person and can range from mild to severe. However, children with Down syndrome have a widely recognized appearance.

The head may be smaller than normal and abnormally shaped. For example, the head may be round with a flat area on the back. The inner corner of the eyes may be rounded instead of pointed.

Common physical signs include:

• Decreased muscle tone at birth
• Excess skin at the nape of the neck
• Flattened nose
• Separated joints between the bones of the skull (sutures)
• Single crease in the palm of the hand
• Small ears
• Small mouth
• Upward slanting eyes
• Wide, short hands with short fingers
• White spots on the colored part of the eye (Brushfield spots)

Physical development is often slower than normal. Most children with Down syndrome never reach their average adult height.

Children may also have delayed mental and social development. Common problems may include:

• Impulsive behavior
• Poor judgment
• Short attention span
• Slow learning

As children with Down syndrome grow and become aware of their limitations, they may also feel frustration and anger.

Many different medical conditions are seen in babies born with Down syndrome, including:

• Birth defects involving the heart, such as an atrial septal defect or ventricular septal defect
• Dementia, Alzheimer's type may be seen
• Eye problems, such as cataracts (most children with Down syndrome need glasses)
• Early and massive vomiting, which may be a sign of a gastrointestinal blockage, such as esophageal atresia and duodenal atresia
• Hearing problems, probably caused by regular ear infections
• Hip problems and risk of dislocation
• Long-term (chronic) constipation problems
• Sleep apnea (because the mouth, throat, and airway are narrowed in children with Down syndrome)
• Teeth that appear later than normal and in a location that may cause problems with chewing
• Underactive thyroid (hypothyroidism)