Causes And Symptoms
While Down syndrome is a chromosomal disorder, a baby is usually identified at birth through observation of a set of common physical characteristics. Babies with Down syndrome tend to be overly quiet, less responsive, with weak, floppy muscles. Furthermore, a number of physical signs may be present. These include:
- flat appearing face
- small head
- flat bridge of the nose
- smaller than normal, low-set nose
- small mouth, with a protruding tongue
- upward slanting eyes
- extra folds of skin located at the inside corner of each eye, near the nose (called epicanthal folds)
- small, outwardly rotated ears
- small, wide hands
- an unusual, deep crease across the center of the palm (called a simian crease)
- a malformed fifth finger
- a wide space between the big and the second toes
- unusual creases on the soles of the feet
- shorter than normal height
Other types of defects often accompany Down syndrome. About one third of all children with Down syndrome have heart defects. These heart defects are characteristic of Down syndrome, including abnormal openings (or holes) in the walls which separate the heart's chambers (atrial septal defect, ventricular septal defect). These defects result in abnormal patterns of blood flow within the heart, resulting in inefficient oxygen delivery.
Malformations of the gastrointestinal tract are present in about 5–7% of children with Down syndrome. The most common malformation is a narrowed, obstructed duodenum (the part of the intestine into which the stomach empties). This disorder, called duodenal atresia, interferes with the baby's milk or formula leaving the stomach and entering the intestine for digestion. The baby often vomits forcibly after feeding, and cannot gain weight appropriately until the defect is surgically repaired.
Other medical conditions occurring in patients with Down syndrome include an increased chance of developing infections, especially ear infections and pneumonia; certain kidney disorders; thyroid disease; hearing loss; vision impairment requiring glasses (corrective lenses); and a 15-fold increased risk for developing leukemia.
Developmental milestones in a child with Down syndrome are delayed. Due to weak, floppy muscles (hypotonia), babies learn to sit up, crawl, and walk much later than their normal peers. Talking is also delayed. The extent of delayed brain development is considered to be mild-to-moderate. Most people with Down syndrome can learn to perform regular tasks and can have relatively easy, jobs (with supervision).
As people with Down syndrome age, they face an increased risk of developing Alzheimer disease, a degenerative disease that affects the brain. This occurs several decades earlier than the risk of developing Alzheimers disease in the general population. As people with Down syndrome age, they also have an increased chance of developing a number of other illnesses, including cataracts, thyroid problems, diabetes, leukemia, and seizure disorders.