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Inherited Disorders and Birth Defects

Translocation of an 18 and 15 chromosone

05/04/2007

Question:

I have a son who has an extra chromosone which is rare translocation of a 15 and 18 chromonse. I have not been able to find much information on this type of chromosone. My son does have developmental delays. He is 11 years old and does not speak. I would appreciate to know any information or if any similiars?

Answer:

It sounds like your son has an unbalanced chromosome rearrangement or what is called an unbalanced translocation and there is either too much or not enough chromosome material.

When chromosomes divide in eggs and sperm, they should divide evenly. However, sometimes two pieces of chromosomes break off and switch places with each other. If all the chromosomal material is present, but rearranged – that is, switched places (translocated) - this person should have no health problems since all the chromosomal material needed is present and functioning properly. This is called a balanced translocation.

But, there can be problems if some of the chromosomal material that was switched is lost or duplicated when the chromosomes broke and the switch took place – then there is extra and / or missing information that can lead to birth defects and cognitive problems such as mental retardation. This is an unbalanced translocation and sounds like the situation for your son.

The specific types of problems or birth defects would depend on the specific areas of the chromosomes that were lost or duplicated in the chromosomes that are translocated and what specific genes are located at these sites. For many unbalanced rearrangements (translocations) it is not possible to predict what abnormalities to expect or how severe they may be until there is a child with that specific chromosomal problem.

If you have not already done so, I would suggest that you speak to the genetic counselor or a geneticist to discuss the specific chromosomal abnormality that your son. These professionals work with cytogenetics - experts regarding chromosomal abnormalities - and may be able to provide you with more detailed information if they know exactly what pieces of chromosome were lost or duplicated.

You can find a genetics center near you at the National Society of Genetic Counselors' Resource Center website below. You may also find the Chromosome Deletion Outreach website helpful for general information about chromosomal abnormalities as well as finding families with similar situations.

Related Resources:

National Society of Genetic Counselors Resource Center
Chromosome Deletion Outreach

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