Health Guide

Down Syndrome Characteristics

Other names :
Mongolism, trisomy 21.


Introduction :
Genetic condition characterised by poor muscle tone, abnormal joint movement, mongoloid shaped face, mental retardation, small nose and other characteristics.


Discovery :
Down was a London physician, who in 1866 first described the condition.


Types :
There are as many different types as there are patients, as all vary to some degree in the severity and characteristics of the syndrome.


Cause :
Down Syndrome is a congenital disease that occurs at the moment of conception, due to the presence of three copies of chromosome 21 instead of two (one from each parent). Thus one of the alternate names for this syndrome is trisomy 21. The other name for the syndrome, Mongolism, comes from the patient’s characteristic facial appearance, which is more like that of the Mongol (Chinese) than European. Contrary to some uninformed opinion, Down syndrome can occur in the Chinese, and is easily identifiable.


Incidence :
Down syndrome occurs at a rate of one in every six hundred births overall, but rises to a rate of two in every hundred for mothers over forty years of age.


Prevention :
There is no method of prevention other than women having their children well before turning forty.


Investigations :
Cells from the child can be examined for characteristic genetic changes to confirm the diagnosis.


Screening :
Diagnosis of the condition in older pregnant women before the birth of the child is possible from the 15th. week of pregnancy by two processes - amniocentesis and chorionic biopsy. In these, samples of cells from the fluid around the baby, or the placenta, are examined under a microscope for the characteristic triple chromosome 21. If this is present, the foetus has Down syndrome.


Course :
The condition can be very easily recognised and diagnosed at birth by observing some of the many characteristics of the syndrome. Infants have poor muscle tone, joints that move further than normal, slanted eyes, a flattened facial appearance, small stature, mental retardation, small nose and a short broad hand. Other characteristics that may be present include a fissured protruding tongue, short neck, widely spaced first and second toes, dry skin, sparse hair, small genitals, small ears, poorly formed teeth, and a squint. Close examination of the hands of these people reveals characteristic finger prints that have a whorl with the loop on the thumb side of the finger tip, only one crease on the palmar surface of the little finger instead of two, a smooth pad at the base of the thumb and a prominent crease across the hand from the web between the thumb and index finger to the other side of the palm.


Treatment :
There is no cure possible, as the abnormal chromosome pattern is present in every cell in the entire body. Treatment involves special education, occupational therapy and physiotherapy. They are otherwise treated medically as normal patients.


Diet :
Some patients have difficulty in eating because of their protruding tongue and require food to be mashed or blended before than can cope with it.


Complications :
Down syndrome patients have a higher incidence of abnormal heart formation, a clouded lens in the eye (cataract), infertility, and leukaemia.


Outcome :
Provided there are no serious heart abnormalities or other complications, the life expectancy of these people is relatively normal. Their intelligence is about 40% that of normal (an IQ of 40), and although there is significant individual variation, almost all require lifelong care from devoted parents, carers or an institution.


Further information :
The Down Syndrome Association has branches in every state offering information and support for the families and carers of people with Down Syndrome.

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