Down Syndrome occurs when a baby has an extra 21st chromosome, meaning that each of their cells contain 47 chromosomes instead of 46 chromosomes like most people. Rarely, though, a child has two cell groupings--some cells have the extra 21st chromosome for a total of 47 chromosomes, while some cells do not have the extra chromosome and have the expected total of 46 chromosomes. Down Syndrome usually leads to mental retardation, usually ranging from mild to moderate in severity. Health problems, including but not limited to heart problems and hearing and vision impairments, may be present, as well as physical features such as poor muscle coordination, flattened face, short neck, and slanted eyes. People with Mosaic Down Syndrome may not to be as severely affected, probably because the cells containing the normal amount of chromosomes have a mitigating effect on the ones that have the extra 21st chromosome. Because it is rarer than Down Syndrome, finding information on Mosaic Down Syndrome can be difficult. Here are some steps to help you get started.
Even though prenatal testing is available, parents usually don't become aware that their child has Down Syndrome until after birth. This is especially likely to be true in the case of Mosaic Down Syndrome, where the signs may be more subtle. If you have reason to suspect that your child has Down or Mosaic Down Syndrome, check with your child's pediatrician.
Step2
If further testing is warranted, a blood test can be done to study the chromosomes. If some cells have an extra 21st chromosome and some don't, a diagnosis of Mosaic Down Syndrome is made. This will probably be described as a percentage. For example, if 20 cells are analyzed and 10 of them have the extra 21st chromosome and 10 don't, this is a level of mosaicism at 50%.
Step3
If the diagnosis of Mosaic Down Syndrome is made, check with your child's pediatrician, who can suggest resources and possibly local support groups for parents of children with disabilities.
Step4
Go online. A couple of good places to start are the International Mosaic Down Syndrome Association website and Mosaic Down Syndrome on the Web. On these sites you will find information about the syndrome and the latest research, helpful links, and personal stories. You can also subscribe to a newsletter and connect with other families affected by Mosaic Down Syndrome through these websites.
Step5
Check with your local school district, even if your child is not yet of school age. She may qualify for an early intervention program.
Tips & Warnings
Blood testing can only determine mosaicism in the blood cell line. It is possible for mosacism to occur across cell lines, such as in skin cells or bone marrow cells, and these can be tested as well. Different parts of the body may have different levels of mosaicism.
People with Down Syndrome and Mosaic Down Syndrome are as diverse any other group of people, each with their own strengths and weaknesses.
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