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Down’s syndrome is a
chromosomal disorder that results when a person inherits all or part of
an extra copy of chromosome 21. The most common chromosomal abnormality
that produces Down’s syndrome (accounting for about 95% of all cases) is Trisomy 21, a defect in which an extra, third copy of chromosome 21 is
present in every cell of the body. People with Down’s syndrome have a
widely recognized characteristic appearance. The head may be smaller
than normal (microcephaly) and abnormally shaped. Prominent facial
features include a flattened nose, protruding tongue, and upward
slanting eyes, the inner corner of the eyes may have a rounded fold of
skin rather than coming to a point. The hands are short and broad with
short fingers and often have a single crease in the palm. Retardation of
normal growth and development is typical and most affected children
never reach average adult height. The average mental age achieved is 8
years old. Congenital heart defects are frequently present. Thyroid
problems (underproduction or overproduction of thyroid hormones) affect
about 10 to 20 % of people with Down’s syndrome, but these problems
respond well to treatment. A lthough people with Down’s syndrome have a
range of learning disabilities, it is now recognized that their
achievements may be most influenced by what is expected of them. This
environmental expectation is probably the most important factor in
determining the educational and vocational potential of people with
Down’s syndrome. |
