Overview:
- Down syndrome is a congenital disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. Down syndrome causes the physical and mental growth to be retarded.
- The physical features and medical conditions associated with Down syndrome vary from a child to another.
- To date, there is no evidence that certain behavioral or environmental factors can trigger the syndrome.
- Children with Down syndrome need to see a doctor every now and then.
- Down syndrome cannot be prevented, but can be detected before delivery (during pregnancy).
Down Syndrome Defined:
Down syndrome is a congenital (non-medical) condition caused by an abnormal chromosomal increase, resulting in an intellectual disability, as well as delays in physical growth. Down syndrome varies in severity among individuals. And there is no evidence that the syndrome is attributable to certain behavioral or environmental factors before or during pregnancy.
Other Names:
Trisomy 21, Mangolism.
Types of Down Syndrome:
- Trisomy 21: About 90% of people with Down syndrome have Trisomy 21. With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.
- Mosaic Down syndrome: This type is rare. It occurs when some of the body cells have 3 copies of chromosome 21, but other cells have the typical two copies of chromosome 21. This mosaic of normal and abnormal cells is caused by abnormal cell division after fertilization.
- Translocation Down syndrome: This type of Down syndrome occurs when a portion of chromosome 21 is attached (translocated) onto another chromosome, before or at conception.
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 results in a wide range of varying mental and physical abnormalities. The cause of existence of such an extra chromosome (whether full or partial) remains unknown to date.
Risk Factors:
- Mother’s age: Older women are at higher risk of abnormal division of chromosomes when they become pregnant, and, hence, are more likely to have a pregnancy affected by Down syndrome;
- Previous child with Down syndrome: Parents who have one child with Down syndrome are at an increased risk (by 1%) of having another child with Down syndrome.
Symptoms:
Although the symptoms of Down syndrome vary from a person to another, there are common features associated with the syndrome, including:
- A flattened face, especially the bridge of the nose;
- Almond-shaped eyes that slant up;
- A short neck, small ears, small hands and feet;
- A tongue that tends to stick out of the mouth;
- Tiny white spots on the iris (colored part) of the eye;
- A single line across the palm of the hand;
- Small pinky fingers that sometimes curve toward the thumb;
- Poor muscles or loose joints;
- Shorter in height.
When to see a doctor?
Children with Down syndrome usually are diagnosed before or at birth. However, if you have any questions regarding your pregnancy or your child's growth and development, talk with your doctor.
Complications:
Persons affected by Down syndrome may experience the following complications:
- Heart defects (such as congenital heart defects);
- Hearing and vision problems;
- Thyroid gland disorders (such as hypothyroidism);
- Infectious diseases (owing to immunodeficiency);
- Spinal problems;
- Mental disorders;
- Hearing loss;
- Sleep apnea;
- Ear infections.
Diagnosis:
Before delivery:
- Screening tests: Diagnostic ultrasound, and blood tests: to measure the levels of certain substances in the pregnant woman's blood.
- Diagnostic tests: In some cases, Down syndrome is diagnosed during pregnancy through the aforementioned screening tests. If this is the case, you might consider more testing to confirm the diagnosis. Diagnostic tests that can identify Down syndrome include:
- Chorionic villus sampling (CVS): A sample is taken from the placenta and used to analyze the fetal chromosomes during the first three months of pregnancy (10-12 weeks).
- Amniocentesis: A sample of the amniotic fluid surrounding the fetus is withdrawn after 15-18 weeks of pregnancy.
CVS and amniocentesis are conducted during pregnancy, in addition to the routine screening tests, on pregnant women of all ages.
After delivery:
After birth, the initial diagnosis of Down syndrome is often based on the baby's appearance and physical features. In such a case, a chromosomal test (called ‘karyotype test’) is often conducted, by taking a blood sample, to confirm diagnosis.
Treatment:
Although there is no specific treatment for Down syndrome, early intervention for infants and children with Down syndrome can make a major difference in improving their quality of life. Because each child with Down syndrome is unique, treatment will depend on individual needs. Also, different stages of life may require different services.
Prevention:
There's no way to prevent Down syndrome. If you're at high risk of having a child with Down syndrome, you may want to consult a genetic counselor before becoming pregnant.
FAQ:
o My child has Down syndrome; how can I cope with that?
When the parents learn their child has Down syndrome, they may experience a range of emotions, including anger and fear. They may not know what to expect, or how to care for a child with a disability. Three steps can be helpful in coping with this situation:
- Look for a team of healthcare providers, teachers and therapists, to provide the best care for your child;
- Seek out support groups among the families who are dealing with the same issues;
- Don't believe the myths associated Down syndrome; most persons with Down syndrome live with their families, go to schools, and have jobs.
o Is Down syndrome inherited?
Down syndrome is NOT inherited; since the main cause has to do with abnormal division of the egg or sperm during fetal development.
Myths & Realities:
o Persons with Down syndrome are incapable of learning.
Reality: Persons with Down syndrome are capable of learning if they have proper incentives.