Celebrating Harrison: Genetic Sequencing Identifies Cause of Rare Disorder, Provides Comfort to Parents
by Tim Harkins - 02/28/13
My third son, Harrison Harkins, lived only a brief nine months on this earth, but he has left a legacy that my family and I hope will help others afflicted with a rare and sometimes unknown disease. This is our way of continuing to celebrate Harrison as he may have had a weak body but his spirit was so strong.
From the beginning, we knew that Harrison was not a typical, healthy baby. Immediately after birth, he was moved to the NICU, starting a wave of anxiety and fear that never seemed to end. When we left the NICU to take Harrison home at 3 weeks, the attending physician provided a grave warning, “things will only get worse from here.” As parents, we were determined to improve Harrison’s quality of life and we wanted to prove that physician wrong. Harrison was small at birth and had what is called “failure to thrive.”
For months we attempted to find help in identifying the cause of his symptoms. Unfortunately, the doctors we saw had no information for us, and the basic mantra was that we would have to wait for Harrison to miss his developmental milestones, turning his head when a loud noise, smiling to his mother, tracking with his eye. We were told that we may have to wait 3 years before we would be able to get a diagnosis.
My frustration grew not only as a parent, but also because I knew of DNA sequencing technologies that could provide a possible answer to us as to what was afflicting Harrison. When I talked to the physicians about using these new DNA sequencing technologies, they looked at us as if we had two heads. This was something they just did not seem to understand. It was at this point that we turned to scientists at Baylor College of Medicine, who were utilizing these new technologies and they agreed to sequence Harrison’s genome as a research project. They sequenced his “exome” which is a subset of your genome and contains all those DNA sequences that “code for genes.” Genes are the blueprints for proteins, and when gens are mutated, their subsequent proteins will not function as they need to.
In addition to sequencing Harrison’s exome, they sequenced mine and Holly’s – Harrison’s mother, and my wife. The basic idea was to find a new mutation (called a “de novo” mutation) that was within Harrison’s DNA but did not exist in either Holly or myself. So it was like a giant subtraction problem as Baylor had to look at close to 25000 possible variants and the easiest way to do this is to remove those variants that occurred in either Holly or myself.
Within a few weeks Baylor had reduced the number of possible variants from 25000 down to about five possible de novo mutations, and with a bit more work, they found the de novo mutation that was afflicting Harrison. The sequence showed that Harrison had a mutation in a gene called ASXL3. Because mutations in a related gene, ASXL1, were known to be responsible for a genetic syndrome called Bohring-Opitz Syndrome (BOS), we thought this might be the cause as Harrison had many of the same symptoms as children with BOS. As a scientist, however, I know you can’t say anything definitively when only one child has been sequenced. I’m thankful Dr. Matthew Bainbridge at Baylor didn’t stop there – he began contacting colleagues around the world, and we found that there were at least three other children with ASXL3 mutations and symptoms similar to Harrison.
So now we know of a new rare disease, and eliminated another of those mysterious unknown genetic diseases. Knowing the genetic cause, we can begin to find potential treatments as well as bring answers to other families. In our case, we learned of Harrison’s genetic cause a few weeks after he had entered hospice. Even though we couldn’t do anything to treat Harrison, the knowledge in itself provided some much needed comfort. It is empowering to know that you have done everything you can to rescue your child and that sometimes Mother Nature just deals us a hand that we cannot win. If you know what is afflicting your child, you can then make more thoughtful decisions to improve their quality of life.
Also, because the sequence revealed that Harrison’s mutation was spontaneous, it means that neither my wife, myself, nor our older sons are carriers. I was able to confidently tell my older sons that they are not at risk for having a baby with the same type of disorder and that they actually had a higher chance of getting struck by lightening than having a child like Harrison.
I think that on Rare Disease Day, it’s important to acknowledge the work that patient advocacy groups do in bringing together patients and their families, empowering many and providing them with a sense of connection and hope. It’s equally important to bear in mind how much more can and needs to be done. Only 25% of genetic diseases are understood, so we have a lot more of work to eliminate these unkwnon disease, and Harrison was an example of doing just that. My family’s story illustrates the benefit of genetic sequencing to deliver answers where none exist, and it is our hope that this technology will become much more widely available in the near future. I would like to see the day when all babies will be sequenced at birth, and provide parents with access to valuable information that will help them obtain the best medical help possible for their children.
We miss Harrison every day and we hope that his short life with us will in some way move the practice of medicine forward. He was a very special baby and we’re so glad he was in our lives.