- Trisomy 21 – Happens due to an error in cell division called non-disjunction. Prior to or at conception, a pair chromosome 21 fails to separate; leading to the replication of extra chromosome in every cell of the body.
- Mosaicism – Occurs when there is a mixture of two types of cells, some containing the usual 46 chromosomes and some containing 47. The cells with 47 chromosomes contain an extra chromosome 21.
- Translocation – Here the total number of chromosomes remain 45, but an additional full or partial copy of chromosome 21 attaches itself to another chromosome, usually chromosome 14.
Although Down syndrome is a genetic disorder, the exact cause of what leads to the random existence of an extra chromosome has not been identified. Some opine that maternal age has a direct correlation with increased incidence of Down syndrome.
Some common physical features of Down syndrome are:
- A flattened face, especially near the bridge of the nose
- Almond-shaped eyes that slant up
- A short neck and small ears
- A tongue that tends to stick out of the mouth
- Tiny white spots on the iris (coloured part) of the eye
- Small hands and feet
- A single line across the palm of the hand (Palmar crease)
- Small fingers that sometimes curve toward the thumb
- Poor muscle tone or loose joints
- Shorter in height as children and adults
- Eye disease like cataracts and requirements for glasses in later life
- Hearing loss (up to 75 percent of people with Down syndrome get affected)
- Obstructive sleep apnea, in which the person’s breathing temporarily stops while asleep (about 50 – 75 percent of people with Down syndrome get affected)
- Heart defects at birth (up to 50 percent people with Down syndrome get affected)
Detection of Down syndrome generally follow these routes:
- Prenatal screening tests – Although they do not confirm whether the baby has Down syndrome or not, they give a probability of the foetus being affected by the syndrome. These tests are non-invasive and generally involve blood tests and an ultrasound.
- Prenatal diagnostic tests – Chorionic villus sampling and amniocentesis are two common diagnostic tests with nearly 100 percent accuracy of diagnosing Down syndrome. They are generally conducted between nine and fourteen weeks, and fifteen and twenty weeks, respectively.
One more test is the Percutaneous umbilical blood sampling test that examines blood from the umbilical cord for genetic information.
- Karyotype – An after-birth chromosomal analysis was done to ascertain whether a baby is suffering from Down syndrome or not. It involves drawing the blood sample from the newborn, and then photographing and grouping the chromosomes by size, number, and shape to detect any abnormalities.
Once detected, the main challenge then lies in accepting and dealing with the possible repercussion associated with Down syndrome. It is a lifelong condition and hence starting off early in coping with the disorders pays off.
A doctor’s advice must be taken first and foremost so that medicines can be prescribed and administered to the baby immediately. Dealing with immediate family and society regarding the disorder, and coming to terms with the realisation may take the considerable amount of time and also professional help from counsellors and psychologists.
Once the baby grows up, questions regarding their speech process, educational services, physical therapy, and occupational opportunities need to be addressed.