Down syndrome is a genetic disease that causes an extra copy of chromosome 21 (either full or partial) because of aberration in cell division. It is also known as trisomy 21. This disease may lead to a disability of mental and physical features.
It is basically not a disorder but a condition that explains the changes in features because of chromosomal abnormalities. The degree of these changes varies from child to child. This disease can’t be prevented but it can be diagnosed. The increased understanding of the disease and advancement in medicine is helping the people with Down syndrome to live their life to the fullest.
What causes down syndrome?
Human cells contain its genetic information in the form of 46 chromosomes. During reproduction, a baby receives 23 chromosomes from the father and 23 from the mother that make up the total of 46 chromosomes or 23 pairs of chromosomes.
In case of down syndrome because of some abnormalities in cell division, chromosome 21 doesn’t separate properly and cell receives an extra or partial copy. So, the baby ends with having three copies of chromosomes instead of two. It leads to the developmental delays and characteristics changes associated with down syndrome.
There is no known obvious reason that why this occurs, but it is associated with father and mother. About 5% of the cases were observed of paternal origin and the risk factor increases with age in the case of mothers.
There are three main types of down syndrome:
Trisomy 21; this is the most common (about 95%). In trisomy 21 there is an extra copy of chromosome 21. The main reason for this condition is the abnormal division in sperm or egg cell development.
Mosaic down syndrome; in this type, there is an only extra copy in some cells while others are normal. It is rare and results because of cell division aberration after fertilization.
Translocation Down syndrome; it occurs when the cell has part of the extra chromosome that is attached to another chromosome with a total of 46 chromosomes. This extra part leads to down syndrome characteristics.
An occurrence of Down syndrome
It has been estimated that 1 of 1000 or 1 of 100 children is born with Down syndrome worldwide. It is most common in united states where about 1 in 700 babies are born with down syndrome according to NDSS (National Down Syndrome Society). So, almost 3,000 to 5,000 children are born with DS in the US.
Characteristics of Down syndrome
People with Down syndrome have varying physical features, mental disabilities and some also suffer from health issues. Most of the babies can be diagnosed by their discrete physical features that are as follows;
- Short neck
- Small head and ears
- Small fingers and small hands and feet
- Flattened face
- Short Stature
- Smallmouth with protruding tongue
- Hypotonia (poor muscle tone)
- Upward slant to the eyes
- Mental disabilities: These vary from mild to moderate and are as follows:
- Affected short and long-term memory
- Slow learning
- Impulsive behavior
- Poor attention
Kids with down syndrome don’t have any medical problem but, in some cases, it may lead to health complication that requires extra attention/care. These include;
- Congenital heart defect (around half of the children with Down syndrome develop this)
- Pulmonary hypertension (may leading cause of damage to lungs that is irreversible)
- Vision problems (cataracts, near or farsightedness, cross-eyed)
- Stomach and intestinal problems (GI blockage, heartburn)
- Increased risk of being obese
- Hearing problems
- Alzheimer’s disease
- Low thyroid function
However, most of these health conditions are curable.
How is a diagnosis of down syndrome is done?
Parentally; Down syndrome can be diagnosed in a baby before its birth in the uterus of the mother by two types of tests that are;
• Screening tests
• Diagnostic tests
Screening tests only give an estimate that a baby will have down syndrome or not. They don’t give surety about the diagnosis of Down syndrome. While on the other hand diagnostics tests give about 99% accurate information.
Blood tests measure the concentration of different substances in the serum of maternal blood. Blood tests are performed along with an ultrasound that reveals the characteristics changes associated with down syndrome. There is another test named ultrasound and QMS (quadruple marker screen). It is performed in the second trimester and tells about abnormalities in the brain and spinal cord.
All these screening tests are costly and inaccurate therefore screening tests are followed by diagnostic tests. Diagnostic tests give a definitive answer, but they are invasive and may cause complications and risk of miscarriage as they are performed in the uterus. These tests include;
- Chorionic villus sampling (CVS); this test involves taking sample/cells from placenta and examining it for fetal chromosomes. This is done in the first trimester between 8 to 12 weeks. But this test may cause miscarriage and some other complications.
- Amniocentesis; in this test, the doctor inserts a needle in the abdomen and take a small sample of amniotic fluid for checking chromosomal abnormalities during 15 to 20 weeks of pregnancy. But the drawback of this test is that it may lead to a small risk of miscarriage.
- Percutaneous umbilical blood sampling (PUBS); this test is also known as cardiocentesis. It involves taking a small sample of blood by inserting in the umbilical cord after 18 weeks of pregnancy. This test also has the same risks as for amniocentesis.
Some of the parents don’t take a risk of having a miscarriage, therefore, they don’t get parenteral screening and diagnostics tests. When a baby is born down syndrome can be identified by their distinct physical characteristics such as the flattened face, upward slant to the eyes, poor muscle tone etc.
There is another test named karyotype that involves taking a blood sample of baby and then examining for chromosome number, size, and shape. This helps in diagnosing down syndrome.
Treating down syndrome
There is no specific treatment available for people suffering from down syndrome. Treatment can only be done for health problems associated along with physical and mental abnormalities. However, children may receive an extra care by providing them support services.
First, if parents come to know that they have a down syndrome child then they may have feelings of guilt and fear. They must have a consultation with other parents having down syndrome child so that they may learn how to get relief from their fears.
Then coming to the down syndrome child, they must be enrolled in the early intervention services that will help them how to survive in the society by participating in the social activities actively. These services have physical therapists, speech therapists and social workers that give the child special education to enhance their language, social, motor, self-help, and sensory skills.
Next question is when to send your down syndrome child to school. Schooling plays a very important role in the life of down syndrome child. Child study team may help you to make the best decisions for your child. Down syndrome child gets a special education that enhances his/her intellectual abilities making it possible to survive.