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The way a person looks and the way his/her body functions come from the genes. They are responsible for everything from your hair colour to regulating the body's tissues and organs. Yes, genes! They are made of DNA and every person has two copies of each gene, one inherited from each parent.
21 March is observed as World Down Syndrome Day and it aims to raise public awareness about this disorder.
What Is Down Syndrome & What Causes It
Each cell in the body comprises of 23 pairs of chromosomes, a total of 46. One chromosome in each pair comes from your mother and the other from your father.
Down syndrome is a genetic disorder which occurs when there is an abnormal cell division resulting in an extra full or partial copy of chromosome 21. This has an effect on the body physically and mentally like impaired physical growth, delayed cognitive ability and a higher risk of some health problems  .
According to the Centers For Disease Control and Prevention, each year about 6,000 babies are born with Down syndrome, which makes it the most common chromosomal disorder.
Types Of Down Syndrome
- Trisomy 21 - It is the most common type of Down syndrome accounting to 95 per cent of Down syndrome cases. Trisomy 21 is caused when each cell has three copies of chromosome 21 instead of two copies 
- Translocation Down Syndrome - This type of syndrome occurs when a partial or full copy of chromosome 21 becomes attached to another chromosome 
- Mosaic Down syndrome - In this type, an individual has two types of cells - those containing 46 chromosomes and those with 47 chromosomes. The cells with 47 chromosomes contain an extra chromosome 21  .
Risk Factors Of Down Syndrome
- Genetic factors - Children can inherit the genetic translocation of Down syndrome from both their parents.
- Mother's increased age - A woman who is above 35 years of age have a higher chance of having a baby with Down syndrome. This is because older eggs have an increased risk of improper chromosome division 
Characteristics Of Down Syndrome
The physical characteristics of a child with Down syndrome  are the following:
- Low muscle tone
- Eyes which are upward slant and white spots on the iris
- Flat nasal bridge and a short neck
- Short height
- Protruding tongue and large spaces between the large and second toe.
There is also a delay in growth and development which includes a defect in speech, delayed development of fine motor skills, and other problems like impulsive behaviour, slow learning, poor judgement, and short attention span  ,  .
Complications Of Down Syndrome
- Congenital heart defect - About half of the children with Down syndrome are born with heart problems.
- Respiratory problems - Children may face respiratory issues due to a narrow airway, tracheal bronchus or weak immunity.
- Sleep apnea - The soft tissues and skeletal changes cause an obstruction in the airways leading to sleep apnea.
- Leukaemia - Children are more likely to have leukaemia, a cancer of the blood or bone marrow.
- Dementia and Alzheimer's disease - Children have an increased risk of dementia and Alzheimer's disease and the symptoms usually begin at around 50.
- Epilepsy - The prevalence of epilepsy is 1 to 13% in people with Down syndrome.
- Gastrointestinal problems - This causes problems in the intestines, trachea, oesophagus and anus.
- Immune disorders - Children have a greater risk of developing autoimmune disorders.
- Obesity - Children with Down syndrome are obese in nature.
- Spinal problems - People have a misalignment of the two vertebrae in the neck causing spinal problems.
- Hearing and vision difficulties - Hear and vision loss is common in children with Down syndrome.
Diagnosis Of Down Syndrome 
Women who have a greater chance of having a child with Down syndrome require screening tests to know whether the foetus is having Down syndrome or not. These screening tests include the following:
- Nuchal translucency testing - In 11 to 14 weeks, an ultrasound is done behind the neck of a developing baby.
- Triple screen or quadruple screen - This test is done in 15 to 18 weeks to measure the quantities of various substances in the mother's blood.
- Genetic ultrasound - In 18 to 20 weeks, an ultrasound is performed along with blood tests.
- Cell-free DNA - A blood test to examine foetal DNA in the mother's blood.
- Integrated screen - This is done in combination with the results of first-trimester blood tests and screening tests.
Screening tests will not confirm the possibilities of a child having Down syndrome.
Diagnostic tests, on the other hand, will provide accurate information in detecting Down syndrome. These tests include the following:
- Amniocentesis - A small amount of amniotic fluid is obtained for examination with the help of a needle inserted into the abdomen.
- Chorionic villus sampling - A small sample of the placenta is analyzed which is obtained from the cervix or abdomen.
- Percutaneous umbilical blood sampling - A tiny sample of blood is taken from the umbilical cord for analysis.
- These diagnostic tests are done inside the uterus which can increase the risk of miscarriage, foetal injury or preterm labour.
Treatment For Down Syndrome
Down syndrome is a lifelong condition and there is no cure for it. Health services can help improve a child's physical and cognitive development in early childhood. These services include the following:
- Speech therapy to improve their speaking skills.
- Primary therapy to aid in growth and development.
- Physical therapy to help strengthen muscles and motor skills.
- Medical specialists like cardiologist, hearing and eye specialist, an endocrinologist for the patients suffering from health problems.
- Behavioural therapy for managing emotional behaviour.
- Occupational therapy to help improve motor skills.
Children who have difficulties in learning and development should seek educational support from specialized schools who can help them progress.
Life Expectancy & Prevention Of Down Syndrome
A person with Down syndrome can live more than 60 years, depending on the severity of his/her health problems  .
Down syndrome can't be prevented. If one parent has this condition, there is a 30 to 50 per cent chance that their children will get it too. It is recommended to consult a genetic counsellor before becoming pregnant.
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