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