Down Syndrome Health Article

Down Syndrome

Also referred to as Down's syndrome or Down's, a genetic disorder present at birth that is caused by an abnormality in the number of chromosomes.

Down syndrome occurs with equal frequency in people of different nationalities, social backgrounds, and economic classes, averaging 1 in about every 600 births. In the United States, over 400,000 people have the condition. Women over 35 are at greater risk of bearing a child with Down syndrome than younger women. One in 1500 children with Down syndrome is born to a mother under 30; for mothers over 45, this figure rises to one in 65. Altogether, though, 80% of all Down infants are actually born to women under 35. According to recent studies, the age of the father may play a role as well. Prenatal detection of Down syndrome is possible through amniocentesis and chorionic villus sampling and is recommended for pregnant women over the age of 35.

John Langdon Haydon Down, a British physician, first described Down syndrome in 1866. In 1959, French pediatrician Jerome Lejeune found that it is caused by a genetic abnormality: an extra chromosome in the 21st pair of chromosomes (trisomy 21). People with Down syndrome have a total of 47 chromosomes instead of the normal 46. The main symptom of Down syndrome is mild to severe mental and motor retardation. Motor, speech, and sexual development are delayed, and cognitive development may not peak until the age of 30 or 40. Most people who have the disorder are severely retarded, with an IQ of between 20 and 49, and prone to a number of physical problems, including hearing and heart defects, poor vision, cataracts, and low resistance to respiratory infections. In the past it was common for children with Down syndrome to die of pneumonia before reaching adulthood. They have a greater than average likelihood of developing leukemia, and many die of a neurological condition similar to Alzheimer's disease by the age of 35. In spite of the discovery of antibiotics and other medical advances, people with Down syndrome still have an average life expectancy of only 16 years and seldom live past the age of 50.

Individuals with Down syndrome have a short, stocky build, with a short neck and a smaller than average skull, usually flat in back. Their most distinctive facial features are the upward-slanting, almond-shaped eyes on which an early name used for the condition—mongolism—was based. Other facial characteristics include a small nose with a flat bridge; a fold of skin (the epicanthal fold) at the inner corner of the eye; a large, protruding tongue (which makes normal speech difficult); and light spots at the edge of the iris (Brushfield spots). The outer ear and chin are generally small. The hands are small, with short fingers, a curved little finger, and a line on the palm called the Simian line. Children and adults with Down syndrome tend to have sweet and docile temperaments; they are generally cheerful, cooperative, affectionate, and relaxed.

Infancy

Wide variations occur in the developmental sequence for children with Down syndrome. On the whole, they go through the same developmental stages as other children but often at a delayed rate. One common characteristic that hampers development in infants with Down syndrome is low muscle tone (hypotonia), characterized by floppy, overly relaxed muscles. Proper muscle tone can be developed eventually with the aid of physical therapy. At the age of one year, most Down infants are able to roll over, sit up by themselves, and support their own weight from a standing position; they can also reach for and pick up objects. Teething may be delayed, and when they do come in, their teeth often appear in an unpredictable order, in contrast to those of most other infants.

Toddlerhood

By the end of their second year, infants with Down syndrome can usually crawl (although many progress straight to walking without crawling at all). Most can stand unassisted and take at least a few steps on their own. They communicate enthusiastically through gestures and simple expressions such as "da-da" and "mama" and imitate the activities of those around them.