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NetWellness provides the highest quality health information and education services created and evaluated by faculty of our partner universities.
Sunday, July 6, 2008
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NetWellness provides the highest quality health information and education services created and evaluated by faculty of our partner universities.
Sunday, July 6, 2008
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Inherited Disorders and Birth Defects |
Balanced translocation t(15;18)02/22/2002 03:59AM |
A friend of mine has a daughter with a balanced translocation t(15,18). The karyotype is 46,XY,t(15;18)(q21.1;q12.2)de novo. We already know that it is a very rare one. We would like to have more information about it, like what the name is of this disorder or the disease caused by it.
Chromosomes are the structures found in the cells of our bodies that hold genes. It is the genes that tell our bodies how to form, function and grow. The genes in each cell are located along the chromosomes - 46 in each cell. Chromosomes come in pairs, 23 of the chromosomes come from the mother and the other 23 come from the father.Chromosomal translocations can be somewhat tricky to understand. A balanced translocation occurs when two pieces of chromosomes break off and switch places with each other. In the situation you describe, it would mean that part of chromosome 15 and part of chromosome 18 have broken off and switched places. If all the chromosomal material is present, just 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 a balanced translocation.
However, if some of the chromosomal material was 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.
The specific types of problems or birth defects would depend on the specific areas of the chromosomes that were lost or duplicated and what 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 describe - even though this is the first time the balanced translocation has occurred (de novo) and wasn`t inherited from either parent, there should be no health problems. However, when your friend`s daughter grows up and wants to have children, she should know that she may have a chance of passing on an unbalanced chromosomal rearrangement. This usually leads to a miscarriage, but occasionally, children are born with these types of rearrangements - and they almost always have problems. There is no other name for these types of rearrangements, except to refer to them as balanced or unbalanced translocations and the chromosome numbers involved..
I would hope your friend has had the opportunity to talk to a geneticist or genetic counselor to ask these questions. If they have not, they can locate a genetics center near them by going to the NSGC resource center website below. The other website, Rare Chromosomal Disorders, has a nice explanation of chromosomal rearrangements in their introduction section.
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Anne Matthews, RN, PhD Director, Genetic Counseling and Family Studies Assistant Professor Department of Genetics School of Medicine Case Western Reserve University |
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