Mongolism, or more appropriately, Down’s syndrome, denotes a group of symptoms that characterize people with a certain chromosomal defect. The condition was named after John Langlon Down, a physician, who, in the mid 19th century, classified mental deficiency according to the physical appearance of patients. One category in his classification was labeled Mongolism because the patients that belonged to this category exhibited what, at that time, comprised the stereotype features of a Mongolian. At present, the term Mongolism is no longer used when referring to Down’s syndrome not only because it is a misnomer but because it puts Mongolians in a bad light.

A normal person has 23 pairs of chromosomes, 22 pairs of these chromosomes are numbered 1-22 while the 23rd pair comprises the sex chromosomes, which are labeled XX in females and XY in males. These chromosomes contain the genes that determine the physical and intellectual characteristics, and to a certain extent, the behavior, of a person.

Most people with Down’s Syndrome have an extra chromosome (located at chromosome pair 21). They have 47 instead of 46 chromosomes. A few however, have only 46 chromosomes but extra material from chromosome 21 is present in some of the chromosomes.

The chromosomal defect seen in Down’s syndrome usually originates during the developmental stages of the gametes (i.e., sperm and ovum), but the cause of the defect is unknown. Numerous scientific reports have suggested a link between the syndrome and many factors including advanced maternal age, viruses, radiation, chemicals and auto immune diseases. But up to now, there is no conclusive evidence to prove that any of these factors when present in the pregnant woman, except for age, increases the risk of conceiving a baby with the disorder.

The incidence of Down’s syndrome in the general population is one for every 800 live births. Contrary to your impression, Down’s syndrome is not associated with pregnancies among elder women alone. A woman can bear a child with the syndrome at any age, but the risk of the abnormality manifesting in a baby increases with increasing maternal, but not paternal, age. The odds for a woman under 30 of bearing a baby with Down's syndrome is less than one in 1,000, but these odds increase to one in 400 for women who become pregnant at age 35. The risks for the disorder continue to increase as a woman ages, so that by age 49, the chance of bearing a child with the disorder is one in 12. If a woman has had a baby with Down’s syndrome, the chance that the next baby will likewise have the defect is about one percent regardless of maternal age.

Down’s syndrome is usually diagnosed at birth although mild cases elude detection until months or years later. Babies with the condition have typical features that include limp muscles, a single crease instead of the three creases on the palm, excess skin folds on the nape, very flexible joints, flat facial profile, eyes that slant upwards, and small, low set ears. Also often present are an open mouth, a protruding tongue, and a flat nose. A blood test called a chromosomal karyotype usually confirms the diagnosis.

In general, people with Down’s syndrome have below normal intelligence. In fact, the condition is the most common cause of mental retardation. The intellectual impairment in Down’s syndrome is often aggravated by the co-existence of other abnormalities (e.g., more than two-third have defective vision and an equal number have hearing defects).

Down’s syndrome patients, however, usually have the willingness to learn and determination to succeed. Most will learn to read and write. Many can become bilingual. A few will be able to cope with normal schooling, but most will need special education.

The life expectancy of persons with Down’s syndrome is shorter than the average person – just 40 years. This can be partly explained by the fact that 50 percent are born with heart defects and a significant percentage with congenital abnormalities of the gastrointestinal tract. Down’s syndrome patients are likewise prone to leukemia and those who grow to adulthood are prone to develop an Alzheimer-like disease (marked by progressive loss of intellectual and vegetative functions) in their fourth and fifth decades of life.