Hi everyone. Today’s post is going to be a bit of a long one. I want to explain something in detail to our friends and family, but also want to make sure I document it well for my own reference in the future. I also hope this contributes to the medical community, or other parents, who may have a similar thing their child is going through.
Early in January, 2016, one of the doctors at John Muir suggested that we may want to get a genetics test for Samuel. They were concerned that he wasn’t pacing as quickly as Jacob or Charlie, and they thought a genetics test would be helpful to rule in or out some things. So they pulled some blood on January 20th and sent it away for a genetics test.
The results took about three weeks to come back, and Dr. Tran finally got them on February 9th. We learned about this as Samuel was in his PDA Ligation surgery. Of course that’s the surgery that not only fixed his Patent Ductus Arteriosus, but also paralyzed his vocal chord. We took her call literally while Samuel was under the knife inside the Benioff Children’s hospital. Kristen and I did the call on my iPhone speakerphone, in a courtyard behind the hospital.
In short, Dr. Tran shared that Samuel had something called a genetic “micro-deletion”. As you may expect, a “micro-deletion” means there’s a small amount of DNA that’s missing. Originally she referred to a broad name of a PARK2 gene, but we got very specific information a bit later. Officially, Samuel is missing 351,219 base pairs in Chromosome 6, sub-section 26. We know this as a 6q26 micro-deletion.
The blood test results that came back show the following:
arr [hg19] 6q26(162,510,973-162,862,192) x1
Heres the breakdown of this reading:
arr – This indicates a chromosome Microarray test was performed
hg19 – This refers to the version of the human genome that was used for the test. As the genome is mapped, more information is available, allowing more exact results.
6 – The chromosome
q26 – The section where the missing material should be
162,510,973-162,862,192 – This is the “from” and “to” material that’s missing.
x1 – This means there’s just one copy of base pairs on each side of the chromosome, as you’d expect.
I’m not billing myself as an expert, but I’ve done a fair amount of research on this topic the past year, looking for answers. As such I’ve learned a lot. Of course you may remember from biology class that each human typically has 46 chromosomes. 23 are from the mom and 23 are from the dad. The last chromosome, Number 23, is an X from the mom and either an X or a Y from the dad that determines what sex you are.
Within each chromosome, there are base pairs of DNA. These are the building blocks and instructions that tell the body what to do, how to grow, etc. There are about 3,000,000,000 (3 Billion) base pairs in each person, spread across those 23 pairs of chromosomes. If you just focus on chromosome 6, there are approximately 171,000,000, or about 5.5% of all the DNA in your body.
Chromosome 6 is also broken into two “arms”. The short arm is called the “p” arm, while the long arm is called the “q” arm. (In case you’re wondering, “p” was chosen as an abbreviation for “petit”, while “q” was chosen because it’s next in the alphabet. Makes little sense to me, but whatever.) The short backstory is that the gap between the “p” and “q” arms is where the chromosome is attached to the spindle during cell division. Let’s not get too medical and just leave it there.
Samuel has his micro-deletion on the long-arm “q” section of chromosome 6, in a sub-section known as 26. There are only 27 sections on this chromosome, so he’s missing some DNA on the far end of this arm. 351,219 base pairs sounds like an awful lot of missing DNA, but remember this is out of 171,000,000 base pairs in this chromosome and 3 billion overall. Specifically, Samuel’s deletion is from base pair number 162,510,973 to 162,862,192.
So what does all this mean?
We’re not entirely sure what all this means yet. I’ve joined groups on Facebook for those who have deletions, and I’ve searched the Internet extensively to see who else is missing this. We’ve talked with a couple geneticists and Samuel, Kristen and I submitted some blood for extensive genetics testing (called Whole Exome Sequencing). Frankly, Kristen and I may end up learning things in this test about our own bodies that may be forecasting future problems like cancer, Alzheimer’s Disease, etc. So we’re a bit frightened to see what comes back.
The blood test results we should get in March will hopefully have some answers, or at least be able to further narrow things down, or be able to tell more definitively what we may have to deal with going forward.
There are all sorts of other children and people who are missing sections of 6q26, though the deletions are much larger (i.e. millions or tens of millions of missing pairs). We’ve also seen examples of people who are missing multiple sections (i.e. 6q26 + 6q27), or who have duplicate genes too. There are many different mutations that we’ve seen. But we haven’t found anybody who has such a tiny deletion, nor have we found anybody with the exact deletion, or reasonably close to the overlap. I posted the specifics on this page in case somebody comes across this and has something similar with themselves or their family. We’d love to talk with you!
Obviously the most interesting thing that Samuel is coping with is his Hypotonia, but since he’s still developing and can’t talk to us yet, we’re not sure what else we may be in store to deal with. We’ve seen others with 6q26 deletions showing symptoms of Autism, inability to speak until various age ranges from 3 or 4 all the way up to not being able to effectively communicate into high school. We’ve seen people who have some deletions who can’t go to the bathroom, have motor skill issues, etc. So we’re not sure what we’re in for.
For now, we continue to work carefully with Samuel on his physical therapy, occupational therapy and speech therapy. He’s showing great signs of progress almost on a weekly basis.
If you know something about this micro-deletion, or know of somebody who has something in 6q26, please feel free to contact us directly. We’d love to hear what your journey is or has been, and happy to share what we know at this point.