210.657.4968
7155 Oakridge Drive
San Antonio, Texas 78229
It's Complicated: 
Beyond Deletions & Duplications
One of the joys of the Annual Registry Conference is that families can meet others who have walked the same path and can relate to their experiences. In fact, the syndrome specific breakouts are some of the most popular sessions at the annual Registry conference. For once, parents can name the diagnosis without having to explain it. Phrases like "distal 18q-" and "tetrasomy 18p" are met with understanding instead of confusion.

However, for some, the question, "What does your child have?" is a complicated one, even among other families with chromosome 18 conditions. That is because their family's chromosome change is more complex than a simple deletion or duplication of a piece of chromosome 18 .

Some individuals have changes on other chromosomes as well as a change on chromosome 18. An unbalanced translocation, for example, could lead to 18q- in addition to a duplication of part of another chromosome. This additional chromosome duplication may cause medical and developmental problems above and beyond those we would expect in someone with "just" 18q-.

Other individuals have more complex rearrangements of chromosome 18, such as a deletion on one arm and a duplication on the other. Again, this makes it difficult to know what to expect for that person, as they have more than one chromosome abnormality.

Lastly, some families have genetic changes that cannot even be interpreted. Using microarray technology, submicroscopic deletions or duplications may be identified on chromosome 18. In some cases, the laboratory may not know whether that change is associated with any health concerns. This is because there is a great deal of variation within the human genome. Much of that variation is "benign". This mean that it is not expected to cause any issues. However, if the lab sees a variation that has not been reported before, they might not know whether or not it is a benign finding. This leads them to call it a "variant of uncertain significance". The family may therefore still not know whether or not this chromosome finding is even relevant.

While the Chromosome 18 Registry & Research Society is always happy to welcome families with complex rearrangements or variants of uncertain significance, there are some other resources that may also be useful, particularly to those families with multiple chromosome changes.

Chromosome Deletion Outreach: www.chromodisorder.org
UNIQUE: The Rare Chromosome Disorder Support Group: www.rarechromo.org

The Chromosome 18 Clinical Research Center is also working hard to understand the implications of microdeletions and microduplications. We are enrolling any families with these findings in the research study. To learn more our research, please click here: https://pediatrics.uthscsa.edu/centers/Chromosome18/index.asp


Courtney Sebold, MS, CGC
Genetic Counselor
Chromosome 18 Clinical Research Center
University of Texas Health Science Center at San Antonio

Best Regards,
 
Leah Gransbery
Manager of Operations
The Chromosome 18 Registry & Research Society
(210) 657-4968 
gransberyl@chromosome18.org 
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