# Handbook of Genetic Counseling/Reciprocal Translocation

Reciprocal Translocation

## Contracting

* What were you told about why you were referred to Genetics?
* What did they tell you about the results of the chromosome studies?
* What are your main concerns? Do you have any questions?
* Overview of session

## Intake

* Follow intake questions
** What doctors are they seeing?
** Has she had any surgeries, or is she scheduled for any?
** What have they been told about the Dandy-Walker malformation and hydrocephalus?
** What have they been told about her heart defect?
** Has anyone talked with them about what to expect in the future?
* Updates to family history?
** Ask again about mental retardation, learning problems, birth defects
** Ask again about miscarriages and stillbirths in family

## Genes and Chromosomes

* Chromosomes are instruction books for bodies - genes located all along chromosomes
* One copy of each from mother, one from father

## Explanation of Chromosomes

* Show her karyotype to parents and point out rearrangement
* This is what we call a reciprocal translocation
* Parts of two different chromosomes break off and redistributed to different chromosomes
* Her chromosomes look a little bit different than what we would expect
** This happens to about 1 in 500 people
** We don't know why this happens sometimes
** This is not something that we can change or fix
** Nothing that anyone did or didn't do caused this to happen - it is a random event

## What Does this Mean

* We don't really know right now - but there are some ways that we can try to find out
* It looks like the translocation is balanced
** All of the genetic material is still there, it is just rearranged (show yellow and pink chromosomes)
** Most of the time, this does not cause a problem so it would not explain why was born with Dandy-Walker malformation and a heart problem
** Remember that there are genes along the length of the chromosomes?
*** There are spaces between those genes
*** If the chromosomes broke in those spaces, it should not have disrupted any genes and all of the body functions should still work
*** We would expect a child with a balanced reciprocal translocation to be healthy
*** This would mean that her health complications are caused by something other than the translocation
** BUT . . .
*** If one or both of the chromosomes broke in the middle of a gene, or if a small piece of one of the chromosomes is missing, that could cause problems (5%)
*** Unfortunately, we can't look any closer at her chromosomes right now, so we can't tell if this is the case
*** If a gene is interrupted or a piece is missing, this COULD explain her problems
** To help us determine whether the translocation is balanced or not, we need to look at BOTH of her parents chromosomes

## Importance of Looking at Parent's Chromosomes

* If you both have normal chromosomes:
** The balanced translocation is something new
** If might explain the Dandy-Walker malformation and heart defect
* If one of you has the same balanced translocation as_____
** We know that you both do NOT have Dandy-Walker malformation or a heart defect
** Because you both don't have any health complications, we know that all of the genetic information is there - nothing is missing or interrupted
** This means that her problems may have another cause

## What Does this Mean for her's Future?

* At this point, it is hard to say
* Once we know more about parents chromosomes, we will have a better idea about what caused the Dandy-Walker malformation and heart defect
** If the translocation does appear to be the cause of the problems, we still may not be able to predict what will happen to her in the future
*** As mentioned before, we can't always look close enough at the chromosomes to know exactly what genes might not be working right
*** We can be sure that her gets the care that she needs, including tests to rule out any possible problems and physical, occupational, speech therapies if needed
** If the translocation is not the cause of the problems, we may be able to identify another cause
** Either way, the important thing is that her gets the medical care that she needs

## Reproductive Risks of a Balanced Reciprocal Translocation

* As we have already talked about, a balanced reciprocal translocation usually does not cause any physical differences
* Does have impact on reproduction
* Four possible outcomes for any pregnancy:
** A child with normal chromosomes
*** Would expect child to be healthy
*** They cannot pass on the translocation to their children
** A child that is a balanced translocation carrier
*** If the parents are healthy, we would expect the child to be too
*** Child would have same four possible outcomes for a pregnancy as we are discussing now
** A child with an unbalanced translocation causing a physical or mental handicap
*** Unbalanced translocation means that there is extra or missing chromosomal material
*** Could lead to physical differences, medical problems like heart defects, etc.
** An unbalanced translocation that leads to miscarriage or stillbirth
*** Usually if the piece that is extra or missing is large (contains a lot of chromosomal material)
*** There are too many changes in genetic material to allow a conception to grow
* Some people with balanced translocations have problems with infertility

## Risk Assessment

* The exact risk assessment depends on where the chromosome breaks
* Overall, there is 5-30% risk to have child born with physical or mental handicaps (general population is 3-5%)
* There is a 20-30% risk for miscarriage (general population 15%)

## Reproductive Options for Balanced Translocation Carrier

* Just be aware of risks
* Prenatal testing - amniocentesis or CVS
* Adoption
* Sperm or egg donor
* PGD or IVF

## Psychosocial

* How do you feel about what we talked about?
* Do you have any new concerns?
* Give patient literature about translocations
* Feelings of guilt or blame if either parent is translocation carrier
* Frustration over inability to offer an explanation right now
* Fear, worry, anxiety about the future

## References

* Blough, R. "Chromosome Abnormalities." Introduction to Genetic Counseling Lecture (2002)
* Buchholz, J. "Genetic Counseling for Autosomal Reciprocal Translocations." Topics in Medical Genetics Lecture (2002).
* Gardner and Sutherland. Chromosome Abnormalities and Genetic Counseling (2000).

## Notes

The information in this outline was last updated in Sept 2002.