Down syndrome is caused by a medical condition wherein a person has three
copies of chromosome 21 within his or her cells. Normally, a person will
only have two chromosomes within his or her cells. Due to this extra chromosome,
there are changes in the orderly development of the body and brain.
There are two kinds of Down syndrome. The reason that this is noteworthy
is that the SSA evaluate them differently. The two are mosaic Down syndrome
and non-mosaic Down syndrome.
If a person has non-mosaic Down syndrome, this means that there is an extra
copy of chromosome 21 in every cell of his or her body. This accounts
for 98% of all people with Down syndrome. Almost every case demonstrates
mental, neurological, and skeletal system impairments. The SSA considers
a person with non-mosaic Down syndrome to be
disabled from birth and eligible to receive Social Security Disability Benefits.
Mosaic Down syndrome when a person has some cells with the normal two copies
of chromosome 21 and other cells with an extra copy of chromosome 21.
Only 1-2 percent of people that have Down syndrome have this form. The
effects on the person vary greatly--some suffer disabling impairments
others have it and it is not detected clinically.