Home HealthTopics Health Centers Reference Library Research
Join us on Facebook Join us on Facebook Share on Facebook

Inherited Disorders and Birth Defects

Birth defect



My son has global delay due to an extra gene on the eighteenth chromosome. Both my husband and myself have been tested and were told this didn`t come from us. There are no signs of global delay on either side of our family. I would like to know how this happened and if thier is a spacific name for this.


There are 432 genes on chromosome 18 that have been found. Changes, called mutations, in some of these genes could lead to a child having global developmental delay. Also, if a gene is duplicated (an extra gene) that can lead to problems in development. Sometimes there is a whole extra chromosome 18, called trisomy 18. This usually causes global delays and often other birth defects as well. You ask excellent questions, however, I cannot tell you what your son has because you need to know the gene that is extra. That information may also help to give you some information about why this happened. Sometimes genes change just in the child and the problem is not inherited from either parent. Unfortunately, there are times we do not know what caused the mutation or change to happen.

If you have not already done so, I would highly recommend that you talk to a geneticist or genetic counselor. They would be able to look at the tests that were done and give you specific information as it relates to your son and your family. You can locate a genetics center near you at the National Society of Genetic Counselors Resource Center listed at the website below.

Related Resources:

National Society of Genetic Counselors Resource Center

For more information:

Go to the Inherited Disorders and Birth Defects health topic, where you can:

Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University