Down Syndrome (DS) is a multisystem chromosomal disorder, which has been recognised to be the leading genetic cause of intellectual disability occurring in approximately one in 650–700 births. In South Africa the incidence of DS is one in 770 births, or one to three per 1000. It affects all races and all economic groups equally.

Down syndrome is not a disease, disorder, defect or medical condition. It is inappropriate and offensive to refer to people with Down syndrome as "afflicted with" or "suffering from" it. Down syndrome itself does not require either treatment or prevention.

• Trisomy 21 (Extra chromosome 21): caused by an error in cell division, which results in an extra chromosome 21 in all cells. Cardiovascular anomalies occurs in 40% of children with DS. In 20% of the recorded trisomy 21 syndrome cases, frequent death occurs due to these abnormalities.
• Mosaic trisomy 21: In 2–4% of cases, the extra chromosome 21 is only present in some cells and then called mosaic trisomy 21.

• Translocation trisomy 21: In 3–4% of cases, material from one chromosome 21 is translocated onto another chromosome. This means cells have two normal chromosomes 21, with additional chromosome 21 material on the translocated chromosome, usually chromosome 14 or 15. Trisomy 21 translocation affects almost every organ system and results in a wide spectrum of constraints, which are based on intellectual disability predisposed to distinct developmental outcomes. Chromosome analysis is necessary to confirm all cases.

This entity of Down syndrome was originally described by John Landon Down, an English physician, in 1862. He was the first to publish an accurate description of a person with Down syndrome, but used the unfortunate term, “mongolian idiocy”. In 1866 the first detailed description of signs and symptoms that affect these individuals were given. However, it was only discovered by Lejeune, Gautier and Turpinin 1959 that trisomy of chromosome 21 was the underlying abnormality in DS. Today, the term Down syndrome is widely accepted and was adopted by the World Health Organisation in 1965. Very little new information has been added to the clinical description of the condition, apart from the description of the single transverse crease in the palm noted by John Langdon Down's son Reginald in 1908, and the characteristic grey spots on the iris of the eye, noted by Brushfield in 1924.

In 1862 Langdon Down examined the palates and tongues of the residents of the mental hospital where he worked. The first indication that he had identified a specific group of patients was when he discovered the unique physical characteristics and speech pathology when they were compared to the other patients in the mental hospital. He even noted that this group of patients responded very well to training, managing better than would be expected.

Face:

• Flat facial profile (dysmorphic features)
• Eyes that slant upwards (up slanting palperbral fissures)
• Folds on the inside of the eyes (epicanthal folds)
• Small nose with a broad, flat bridge
• Small mouth with protruding tongue (tongue appears large)
• Excess skin on back of neck (loose skin folds)
• Small low set ears

Hands and Feet:

• Single palmar crease (single line) on the palm of the hand
• Broad hands with short fingers
• Inclining pinkie (clinodactyly), brachymesophalangy of the fifth finger
• Gap between the big toe and second toe (sandle gap)
• Slightly shorter arms

Intellect:

• Most individuals with DS have a mild (IQ 50–70) to moderate (IQ 35–50) range of intellectual disability
• Individuals having Mosaic DS typically IQ scoring 10 to 30 points higher
• Developmental delay

Challenges:

• Cognitive development
• Language development
• Motor development
• Sensory development
• Social development

Other:

• Low muscle tone (hypotonia)
• Poor Moro reflex
• Unusual looseness of the joints (Hyper-extensibility of joints)
• Dysplasia of pelvis (hip)
• Neuromuscular and musculoskeletal characteristics may result in developmental delay
• Cardiovascular anomalies (defects) occur in 40% of children with DS
• Eye defects occur in 60% of children with DS
• Hearing defects may occur and may affect speech and language
• Thyroid deficiency and leukemia, are more common in people without DS

Down syndrome can occur in any family. It is not caused by food or medication or any other event. No one is to blame or should feel guilty.

However, the risk to have a baby with DS has been shown to increase with the age of the mother. For a woman who is 20 years of age, the risk may be 1 in 1700, while for a woman of 40 years of age, the risk may be 1 in 100. Although the risk of having a child with DS is less for young mothers than for older women, babies with DS are also born to young mothers.

Down syndrome can be detected in the unborn baby. Different test can be performed to advise the parents of the status of the baby. Tests include a maternal blood screening test, ultrasound, amniocentesis, chorionic villus sampling and cordocenteses. These tests are performed at different stages of the pregnancy and there are different compilations associated with each test.

It is essential that any test should only be performed after genetic counselling. Only after all the facts, risks and consequences have been fully discussed an informed discussion can be made by parents.

There is currently no cure for DS. However, there is much that can be done to assist and help with challenges of the baby with DS.

• Early referral for the detection of complications (heart, hearing and eye defects) is encouraged
• Early intervention
• Stimulation programme such as the ‘Developmental Resource Stimulation Programme’ (DRSP) for child with DS younger than 42 months to reach his/her full potential.