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Chromosomal Microarray Testing

In Patients with Development Delay, Autism or other Congenital Anomalies



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Post-Test Follow-Up

Slide 15

September 2011

Recurrence-risk information is critical and can be a highly complex discussion. This is a topic that a genetics professional should certainly be consulted on given the types of unique rearrangements and difficulties that incomplete penetrance and variable expressivity pose.

The type of anomaly impacts recurrence risk. For example, almost all reciprocal translocations are unique to a family and there is likely no empiric data available to calculate a risk number specific to a particular family’s rearrangement. Therefore, recurrence-risk estimates need to consider the parents’ pregnancy history and family history as well as the size of the regions potentially involved in the various possible unbalanced gametes and whether the literature contains reports of individuals born with imbalances of these regions. And for parents who carry a balanced insertional translocation there is a recurrence risk of 50% for each pregnancy.

For isolated or independent imbalances, recurrence risk information usually depends on whether the imbalance is inherited or is de novo. Generally the risk of a de novo imbalance is low, though not 0% due to possible gonadal mosaicism. If a parent carries an imbalance, each pregnancy would be at 50% risk for inheriting it. However, the actual risk of an abnormal phenotype depends on the likelihood that the imbalance is actually pathogenic as well as factors such as penetrance and the range of variable expressivity.

Post-Test Follow-Up

 


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