Characteristic features of the most common congenital syndromes

JAKARTA (JP): Down's syndrome is one of the most common congenital syndromes.

According to Dr. Mark Selikowitz from Australia, Down's syndrome is the most prevalent chromosomal disorder as well as the most frequent cause of intellectual disability.

In his book Down Syndrome, the Facts, he writes that Down's syndrome occurs approximately once in every 700 births, in all ethnic groups. For reasons still unknown to experts, there are slightly more boys born with Down's syndrome than girls.

The earliest recorded representation of a person with the characteristic features of the condition dates back to an altar- piece in Aachen, Germany, painted in about 1505. But Down's syndrome does not seem to have been recognized until l866, when an British doctor, Dr. John Langdon Down (l828-l896), first described the characteristic features of the syndrome.

Down did not understand the cause of the condition he had described. His suggestion that Down's syndrome was a reversion to "primitive" Mongolian ethnic stock was soon repudiated by his son, Reginald, who was also a doctor, Selikowitz writes.

In l959, 93 years after Down's original description, Lejeune and his colleagues in Paris demonstrated that Down's syndrome was associated with an extra chromosome.

People with Down's syndrome were once referred to as having "mongolism" or being Mongols. These terms came up because of the superficial resemblance between the appearance of people with Down's syndrome and that of Oriental people. Such terms are now out-of-date.

The chance of a woman having a child with Down syndrome increases with her age at the time of conception. The increase is particularly marked from around the age of 35.

In many developed countries, pregnancies in women over 35 constitute less than 10 percent of all pregnancies. It is for this reason that despite increased individual risk, women over 35 give birth to only one-third of all children with the syndrome. It is, therefore, a misconception to think that children with Down's syndrome are only born to older women. In fact, two-thirds of all children with the syndrome are born to mothers under 35, with 20 percent of all children with the syndrome born to mothers who are under 25.

When parents are told that their new-born baby has Down's syndrome, one of the first questions they ask is "How did this happen?"

Down's syndrome results from an extra chromosome 21. This additional chromosome causes an excessive amount of certain proteins to be formed in the cells. This disturbs normal growth in the body of the fetus. The proteins involved and how they act are not yet known.

As the fetus develops, the body cells do not divide as rapidly as they normally do, and this results in fewer body cells, and therefore a smaller baby. In addition, the migration of cells that occurs in the formation of different parts of the body is disrupted, notably in the brain. Once a baby with Down's syndrome is born, all these differences are already present. The baby, having fewer brain cells and a different brain formation, will learn slowly. These deviations are established before birth and cannot be reversed afterwards.

Features

The following are certain characteristic features of Down's syndrome which are useful in recognizing whether a child has the syndrome.

Face: A child with Down's syndrome usually has a rounded face. From the side, the face tends to have a flat profile.

Head: The back of the head is slightly flattened in most people with Down's syndrome. This is known as brachycephaly.

Eyes: The eyes of nearly all children and adults with Down's syndrome slant slightly upwards. In addition, there is often a small fold of skin that runs vertically between the inner corner of the eye and the bridge of the nose.

The eyes may have white or light-yellow speckling around the rim of the iris (the colored part of the eye). These specks are called Brushfield spots, after an English doctor, Dr. T. Brushfield (l858-l937). These spots may also be present in the eyes of normal children. They often disappear later if the iris turns brown. Like the epicanthic folds, they do not interfere with vision.

Hair: The hair of children with Down's syndrome is usually soft and straight.

Neck: New-born babies with Down's syndrome may have excess skin over the back of the neck, but this is usually taken up as they grow.

Mouth: The mouth cavity is slightly smaller than average, and the tongue slightly larger. This combination encourages some children to acquire the habit of sticking out their tongues at times.

Hands: The hands tend to be broad, with short fingers. The little finger sometimes has only one joint instead of the usual two. The palm may have only one crease across it or if there are two, both may extend right across the hand.

Feet: These tend to be stubby, and to have a wide space between the first and second toes. This may be associated with a short crease on the sole, which starts at this gap and runs back for a couple of centimeters.

Development

A child with Down's syndrome will be able to develop and learn throughout his life. From a new-born baby, totally dependent on his parents, he will develop physically, intellectually and emotionally and become more competent with every passing year. Children with Down's syndrome always progress in their development, but do so at a slower rate than normal children.

The eventual aim of childhood development for both normal children and those with Down's syndrome is to gain independence. In all adults, independence is a relative term. In Down's syndrome, development is not only slower than normal, but is also less complete and in adulthood people with the syndrome will need more help than the average person. (raw)