Down syndrome is also known as Trisomy 21. It is a genetic disorder in which an extra copy of chromosome 21 causes life long mental retardation, developmental delays and other problems. It is the most common genetic cause of learning disabilities in children. It affects 1 in every 800 babies born in the United States. Severity of the disease range from mild or moderate to serious with some children needing more medical attention than others. People with Down Syndrome may have other health issues like heart disease, intestinal abnormalities, seizure disorders, respiratory problems, obesity and an increased susceptibility to infections. There is no way of preventing this disease but research shows that the chance of having a child with down syndrome increases with age. This disease cannot be cured but resources are available to make life comfortable for both victims and caregivers. Down syndrome is not inherited. It is caused by abnormal cell division during egg cell and sperm cell development.
Babies normally inherit genetic material from both parents. Human cells have 23 pairs of chromosomes. One chromosome in each pair comes from the mother and the other from the father. In some cases a baby may inherit an extra copy of chromosome 21 and this results in the baby having the disease thus the name trisomy 21.
Down syndrome may be divided into three types depending on how the extra genetic material is acquired.
Trisomy 21 : This is the most common affecting about 95% of individuals. The child has 3 copies of chromosome 21 instead of the usual 2. It is caused by abnormal division during egg cell and sperm cell division.
Mosaic down syndrome : This is a rare form. It occurs when a child inherits an extra copy of chromosome 21 in some cells but not others. These individuals may not have all the typical features of people with trisomy 21 and their condition may not be as severe. This type is caused by abnormal division after fertilization.
Translocation down syndrome : These individuals do not inherit the entire chromosome 21. They just inherit some extra chromosome 21 attached to another chromosome usually chromosome 14. This type is uncommon.
Some people are at a higher risk of having children with Down Syndrome than others.
The main risk factor of having a child with the disease is advanced maternal age. A woman’s risk of having a baby with Down Syndrome increases because older eggs are more likely to experience improper chromosomal cell division.
- 25 years 1 in 1,250
- 30 years 1 in 1,000
- 35 years 1 in 400
- 40 years 1 in 100
- 45 years 1 in 30
If you already have a child with Down Syndrome, there is the likelihood of having another baby with the disease. Also parents can pass on the genetic translocation for Down Syndrome to their children if they are carriers.
Most children with Down Syndrome have distinct physical characteristics. These include the following :
- flattened facial features
- short neck
- protruding tongue
- upward slanting eyes that may have small skin folds at the inner corner
- unusually shaped ears
- small head
- poor muscle tone and loose ligaments
- relatively short fingers
- broad short hands with a single crease in the palm
- white spots on the colored part of the eye
- excessive flexibility
Development and growth may usually be delayed. They are usually shorter than children of the same age. They usually reach milestones such as sitting, crawling and walking later than other children. They have delays in speech and self-care such as feeding, toileting and dressing.
TEST AND DIANGONSIS
The American Congress of Obstetrician and Gynecologists recommends offering various screening tests for Down Syndrome to all pregnant women regardless of their age. This helps parents make important decisions and prepare for caring for a child with special needs. It should be noted that these tests are not 100 % accurate. Some of these tests may also cause a miscarriage.
Ultrasound : It is used to measure a specific region on the back of a baby’s neck. More fluid than usual tends to collect in these tissues when abnormalities exist. This test is known as nuchal translucency screening test.
Blood Test : It measures the levels of pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (HCG). Abnormal levels may indicate a problem with the baby.
Amniocentesis : It is performed between 16 and 20 weeks of pregnancy. A thin needle is inserted through the abdominal wall and a small sample of amniotic fluid is taken. The sample is then used to analyze the chromosomes of the fetus. This procedure carries a risk of miscarriage.
Chorionic villus sampling (CVS) : This is usually done at 11-12 weeks of pregnancy. Collection of chorionic villus cell sample from the placenta is done to analyze fetal chromosome deviations. This test also carries a risk of miscarriage.
Percutaneous umbilical blood sampling (PUBS) : Fetal blood is taken from the umbilical cord. The procedure is done by inserting a needle through the abdominal wall. The procedure is usually done around 18 weeks of pregnancy. It carries a greater risk of miscarriage than amniocentesis and CVS. It is done when previous test results are not clear.
At birth, the initial diagnosis of Down Syndrome is usually based on baby’s facial appearance. You doctor will order chromosomal karyotype to confirm Down Syndrome.
There is no cure for Down Syndrome. Early intervention programs and regular medical check-ups for associated health issues may help one manage the disease well.
Children with the disease should be enrolled in specialized programs that will help them develop their sensory, motor and cognitive skills . Early intervention programs include physical therapy, occupational therapy and speech therapy. They should also be included in family activities.
Corrective surgery may be done for heart defects and other associated health issues that the child may have.
Regular check-ups to screen the child for other diseases is also essential.
People with Down Syndrome may have a wide variety of complications, some of which include the following :
- heart defects
- infectious disease
- respiratory infections
- sleep apnea
- hearing loss
- poor vision
There is no way of preventing Down Syndrome. If you fall into the high risk category of having a child with the disease, it is better to consult a genetic counselor before getting pregnant. The genetic counselor will explain to you prenatal testing available for the disease and what to expects when you have a child with the disease