Ask an Expert: Translocational Chromosomal Disorder

Inherited Disorders and Birth Defects

Translocational Chromosomal Disorder
07/10/2007

Question:

I have a question about chromosomal disorder..I could not find that in list of Health Topics. Have there been reported cases of a child being born with the 5:15 switched? I know for sure that it causes severe mental retardation. What were some of the other symptoms or outcome? Where could I go to find more information on this disorder?

Answer:

In looking at the Chromosome Deletion Outreach support group website, in the Registered Disorders heading, under translocations - at least one case for a 5 and 15 unbalanced translocation is listed. These cases come from all over the world. Members of the support group can register and list the chromosome finding of their child.
As you may be aware, chromosome translocations occurs when two pieces of chromosomes break off and switch places with each other. If all the chromosomal material is present, just rearranged – that is, switched places (translocated) - it is called a balanced translocation. The person with a balanced chromosomal translocation should have no health problems since all the chromosomal material needed is present and functioning properly. There is no way to tell whether or not a person has one of these rearrangements unless you look at his or her blood to examine the chromosomes.
However, 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.
The specific types of problems or birth defects seen 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; for others the medical literature may provide information.
In the situation you mention, you would need to know specifically where on chromosomes 5 and 15 the translocation occurred and how much chromosome material was lost or gained and what genes are located at these sites to be able to provide any additional information. A geneticist or genetic counselor may be able to provide additional information.

Related Resources:

National Society of Genetic Counselors Resource Center

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Response by:

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