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Down's syndrome diagnosis

Down's syndrome (or Down syndrome) is a chromosomal disorder where the affected individual will have a number of abnormal physical and mental characteristics. The most significant characteristic is the considerable learning difficulties that the affected person has. A Down's syndrome individual rarely develops a mental age above that of a five year-old.

Physical characteristics of a Down's syndrome baby

The head tends to be flat-ish, both in the front and the back. The eyes are slanted (hence the older term 'mongoloid') and the ears have a square-ish appearance and are rather low-set.

The arms may appear slightly short and there may be abnormal creases on the palms of the hands. The tongue tends to appear rather too large for the mouth.

Apart from the external physical features, a Down's baby may be born with major internal organ abnormalities. Organs particularly affected are the heart and the gut. Some abnormalities could be life-threatening or require major corrective surgery.

Long term prognosis of a Down's syndrome baby

Apart from the learning difficulties of variable severity, physically a Down's syndrome individual tends to be of short stature. Most of them attain a maximum height of less than five feet (152 cm). Many are a lot shorter than this.

Causes of Down's syndrome (Trisomy 21)

This is a chromosomal disorder.

A normal individual has 23 pairs of chromosomes, making a total of 46 chromosomes. Each and every cell in the body, except for gametes, has forty six chromosomes. In Down's syndrome, there are forty-seven chromosomes. The extra chromosome is on pair number twenty-one. This means on number 21 there are three instead of two chromosomes. This is why this condition is also called Trisomy 21. There are other chromosomal disorders where there is an extra chromosome, as we shall see shortly. Down's syndrome or Trisomy 21 is the most common chromosomal disorder compatible with life.

Predisposing factors for Down’s syndrome

It is important to be aware that most Down’s syndrome babies are born to mothers who have no identifiable predisposing factors. This means that without screening tests, all these will come as a complete surprise. However, there are people who are more likely to have Down’s syndrome children because of a number of factors. The most important factor is maternal age.