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Inherited Disorders and Birth Defects

Balanced reciprocal translocation of 2;6

06/10/2008

Question:

My daughter was born with a balanced reciprocal translocation between the long arm of one chromosome 2 and the short arm of one chromosome 6. There is nothing extra and nothing missing. Upon further testing we found out that my husband is a carrier and apparently has the exact same balanced translocation. I was wondering if there were any studies done in children after birth to determine what exactly this means or what obstacles she may encounter in life, if any. At the present time she is a healthy 2 1/2 year old with advanced vocabulary and learning skills. Thank you

Answer:

Your daughter and husband have what is called a reciprocal balanced translocation which happens when two different chromosomes brake and exchanges pieces of chromosome material and no chromosomal material is missing or added. In your family’s case, that is between chromosome 2 and 6. If all of the chromosomal material is present, although rearranged, you would expect that person to have no problems due to the balanced translocation - this is the case for your husband. Because your daughter inherited the same translocation from her father, you would also expect that there would be no health or developmental problems due to the translocation. If your daughter is healthy and developing normally at this time, you would not expect any health problems arising due to the translocation.

However, for you and your husband if you have additional children as well as for your daughter, there is a risk of passing on an unbalanced rearrangement (where chromosomal material is deleted (missing) or duplicated (added). This situation can lead to problems.

In theory, there is a 25% chance that the gametes (eggs or sperm) that the mom or dad produces – will have a normal chromosome complement, a 25% chance that the egg or sperm will have the balanced translocation (like your husband and daughter) and a 50% chance that the egg or sperm would produce an unbalanced chromosome complement. Usually the eggs or sperm that produce an unbalanced complement are miscarried or cause birth defects, mental retardation and other problems.

I would recommend that you speak to a genetic counselor if you consider having additional children to re-discuss your chances of having a pregnancy with an unbalanced chromosomal translocation. When your daughter gets to child bearing age, she also should talk to a genetic counselor to discuss her chances of miscarriage or having a pregnancy with an unbalanced translocation.

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Response by:

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