Down’s syndrome
Down syndrome is a genetic disorder and the most common autosomal chromosome abnormality in humans, where extra genetic material from chromosome 21 is transferred to a newly formed embryo. These extra genes and DNA cause changes in development of the embryo and fetus resulting in physical and mental abnormalities. Each patient is unique and there can be great variability in the severity of symptoms.
Causes
Human cells normally contain 23 pairs of chromosomes. One chromosome in each pair comes from your father, the other from your mother.
Down syndrome results when abnormal cell division involving chromosome 21 occurs. These cell division abnormalities result in an extra partial or full chromosome 21. This extra genetic material is responsible for the characteristic features and developmental problems of Down syndrome. Any one of three genetic variations can cause Down syndrome:
- Trisomy 21. About 95 percent of the time, Down syndrome is caused by trisomy 21 — the person has three copies of chromosome 21, instead of the usual two copies, in all cells. This is caused by abnormal cell division during the development of the sperm cell or the egg cell.
- Mosaic Down syndrome. In this rare form of Down syndrome, a person has only some cells with an extra copy of chromosome 21. This mosaic of normal and abnormal cells is caused by abnormal cell division after fertilization.
- Translocation Down syndrome. Down syndrome can also occur when a portion of chromosome 21 becomes attached (translocated) onto another chromosome, before or at conception. These children have the usual two copies of chromosome 21, but they also have additional genetic material from chromosome 21 attached to another chromosome.
Signs and Symptoms
Each person with Down syndrome is an individual — intellectual and developmental problems may be mild, moderate or severe. Some people are healthy while others have significant health problems such as
- Serious heart problems
- Flattened face
- Small head
- Short neck
- Protruding tongue
- Upward slanting eye lids (palpebral fissures)
- 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’s 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.
Intellectual disabilities
Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected.
Diagnosis
Health care providers can check for Down syndrome during pregnancy or after a child is born.
There are two types of tests for Down syndrome during pregnancy:
- Screening tests can indicate the likelihood or chances that a mother is carrying a baby with Down syndrome. But these tests can’t tell for sure or diagnose whether the baby has Down syndrome.
- Diagnostic tests can identify or diagnose whether your baby has Down syndrome
Chromosomal Testing of Maternal Blood
A pregnant woman who is at risk for having an infant with Down syndrome also can have a chromosomal test using her blood. A mother’s blood carries DNA from the fetus, which may show extra chromosome 21 material. A more invasive test then would usually confirm the blood test
Diagnosis of Down Syndrome After Birth
A diagnosis of Down syndrome after birth is often based initially on physical signs of the syndrome.
But because individuals with Down syndrome may not have these symptoms, and because many of these symptoms are common in the general population, the health care provider will take a sample of the baby’s blood to confirm the diagnosis. The blood sample is analyzed to determine the number of the baby’s chromosomes.
Treatment
Down Syndrome cannot be cured. However, early treatment can help many people with Down Syndrome to live productive lives well into adulthood.
Children with Down Syndrome can often benefit from speech therapy, occupational therapy, and exercises to help improve their motor skills. They might also be helped by special education and attention at school.
Some of the medical problems common in people with Down Syndrome, like cataracts, hearing problems, thyroid problems, and seizure disorders, can be also treated or corrected.
It has been suggested that children with Down Syndrome might benefit from medical treatment that includes amino acid supplements and or some other drugs to improve the ability of the brain to learn and understand.