When doctors couldn’t stop her daughter’s seizures, this mom earned a PhD and found a treatment herself.
Savannah Salazar (left) and her mother, Tracy Dixon-Salazaar, who earned a PhD in neurobiology in the quest for a treatment of her daughter's seizure disorder.
Twenty-eight years ago, Tracy Dixon-Salazaar woke to the sound of her daughter, two-year-old Savannah, in the midst of a medical emergency.
“I entered [Savannah’s room] to see her tiny little body jerking about violently in her bed,” Tracy said in an interview. “I thought she was choking.” When she and her husband frantically called 911, the paramedic told them it was likely that Savannah had had a seizure—a term neither Tracy nor her husband had ever heard before.
Over the next several years, Savannah’s seizures continued and worsened. By age five Savannah was having seizures dozens of times each day, and her parents noticed significant developmental delays. Savannah was unable to use the restroom and functioned more like a toddler than a five-year-old.
Doctors were mystified: Tracy and her husband had no family history of seizures, and there was no event—such as an injury or infection—that could have caused them. Doctors were also confused as to why Savannah’s seizures were happening so frequently despite trying different seizure medications.
Doctors eventually diagnosed Savannah with Lennox-Gaustaut Syndrome, or LGS, an epilepsy disorder with no cure and a poor prognosis. People with LGS are often resistant to several kinds of anti-seizure medications, and often suffer from developmental delays and behavioral problems. People with LGS also have a higher chance of injury as well as a higher chance of sudden unexpected death (SUDEP) due to the frequent seizures. In about 70 percent of cases, LGS has an identifiable cause such as a brain injury or genetic syndrome. In about 30 percent of cases, however, the cause is unknown.
Watching her daughter struggle through repeated seizures was devastating to Tracy and the rest of the family.
“This disease, it comes into your life. It’s uninvited. It’s unannounced and it takes over every aspect of your daily life,” said Tracy in an interview with Today.com. “Plus it’s attacking the thing that is most precious to you—your kid.”
Desperate to find some answers, Tracy began combing the medical literature for information about epilepsy and LGS. She enrolled in college courses to better understand the papers she was reading.
“Ironically, I thought I needed to go to college to take English classes to understand these papers—but soon learned it wasn’t English classes I needed, It was science,” Tracy said. When she took her first college science course, Tracy says, she “fell in love with the subject.”
Tracy was now a caregiver to Savannah, who continued to have hundreds of seizures a month, as well as a full-time student, studying late into the night and while her kids were at school, using classwork as “an outlet for the pain.”
“I couldn’t help my daughter,” Tracy said. “Studying was something I could do.”
Twelve years later, Tracy had earned a PhD in neurobiology.
After her post-doctoral training, Tracy started working at a lab that explored the genetics of epilepsy. Savannah’s doctors hadn’t found a genetic cause for her seizures, so Tracy decided to sequence her genome again to check for other abnormalities—and what she found was life-changing.
Tracy discovered that Savannah had a calcium channel mutation, meaning that too much calcium was passing through Savannah’s neural pathways, leading to seizures. The information made sense to Tracy: Anti-seizure medications often leech calcium from a person’s bones. When doctors had prescribed Savannah calcium supplements in the past to counteract these effects, her seizures had gotten worse every time she took the medication. Tracy took her discovery to Savannah’s doctor, who agreed to prescribe her a calcium blocker.
The change in Savannah was almost immediate.
Within two weeks, Savannah’s seizures had decreased by 95 percent. Once on a daily seven-drug regimen, she was soon weaned to just four, and then three. Amazingly, Tracy started to notice changes in Savannah’s personality and development, too.
“She just exploded in her personality and her talking and her walking and her potty training and oh my gosh she is just so sassy,” Tracy said in an interview.
Since starting the calcium blocker eleven years ago, Savannah has continued to make enormous strides. Though still unable to read or write, Savannah enjoys puzzles and social media. She’s “obsessed” with boys, says Tracy. And while Tracy suspects she’ll never be able to live independently, she and her daughter can now share more “normal” moments—something she never anticipated at the start of Savannah’s journey with LGS. While preparing for an event, Savannah helped Tracy get ready.
“We picked out a dress and it was the first time in our lives that we did something normal as a mother and a daughter,” she said. “It was pretty cool.”
Genome Reading and Editing Tools for All
An open book representing the ability to read the human genome.
In 2006, the cover of Scientific American was "Know Your DNA" and the inside story was "Genomes for All." Today, we are closer to that goal than ever. Making it affordable for everyone to understand and change their DNA will fundamentally alter how we manage diseases, how we conduct clinical research, and even how we select a mate.
A frequent line of questions on the topic of making genome reading affordable is: Do we need to read the whole genome in order to accurately predict disease risk?
Since 2006, we have driven the cost of reading a human genome down from $3 billion to $600. To aid interpretation and research to produce new diagnostics and therapeutics, my research team at Harvard initiated the Personal Genome Project and later, Openhumans.org. This has demonstrated international informed consent for human genomes, and diverse environmental and trait data can be distributed freely. This is done with no strings attached in a manner analogous to Wikipedia. Cell lines from that project are similarly freely available for experiments on synthetic biology, gene therapy and human developmental biology. DNA from those cells have been chosen by the US National Institute of Standards and Technology and the Food and Drug Administration to be the key federal standards for the human genome.
A frequent line of questions on the topic of making genome reading affordable is: Do we need to read the whole genome in order to accurately predict disease risk? Can we just do most commonly varying parts of the genome, which constitute only a tiny fraction of a percent? Or just the most important parts encoding the proteins or 'exome,' which constitute about one percent of the genome? The commonly varying parts of the genome are poor predictors of serious genetic diseases and the exomes don't detect DNA rearrangements which often wipe out gene function when they occur in non-coding regions within genes. Since the cost of the exome is not one percent of the whole genome cost, but nearly identical ($600), missing an impactful category of mutants is really not worth it. So the answer is yes, we should read the whole genome to glean comprehensively meaningful information.
In parallel to the reading revolution, we have dropped the price of DNA synthesis by a similar million-fold and made genome editing tools close to free.
WRITING
In parallel to the reading revolution, we have dropped the price of DNA synthesis by a similar million-fold and made genome editing tools like CRISPR, TALE and MAGE close to free by distributing them through the non-profit Addgene.org. Gene therapies are already curing blindness in children and cancer in adults, and hopefully soon infectious diseases and hemoglobin diseases like sickle cell anemia. Nevertheless, gene therapies are (so far) the most expensive class of drugs in history (about $1 million dollars per dose).
This is in large part because the costs of proving safety and efficacy in a randomized clinical trial are high and that cost is spread out only over the people that benefit (aka the denominator). Striking growth is evident in such expensive hyper-personalized therapies ever since the "Orphan Drug Act of 1983." For the most common disease, aging (which kills 90 percent of people in wealthy regions of the world), the denominator is maximal and the cost of the drugs should be low as genetic interventions to combat aging become available in the next ten years. But what can we do about rarer diseases with cheap access to genome reading and editing tools? Try to prevent them in the first place.
A huge fraction of these births is preventable if unaffected carriers of such diseases do not mate.
ARITHMETIC
While the cost of reading has plummeted, the value of knowing your genome is higher than ever. About 5 percent of births result in extreme medical trauma over a person's lifetime due to rare genetic diseases. Even without gene therapy, these cost the family and society more than a million dollars in drugs, diagnostics and instruments, extra general care, loss of income for the affected individual and other family members, plus pain and anxiety of the "medical odyssey" often via dozens of mystified physicians. A huge fraction of these births is preventable if unaffected carriers of such diseases do not mate.
The non-profit genetic screening organization, Dor Yeshorim (established in 1983), has shown that this is feasible by testing for Tay–Sachs disease, Familial dysautonomia, Cystic fibrosis, Canavan disease, Glycogen storage disease (type 1), Fanconi anemia (type C), Bloom syndrome, Niemann–Pick disease, Mucolipidosis type IV. This is often done at the pre-marital, matchmaking phase, which can reduce the frequency of natural or induced abortions. Such matchmaking can be done in such a way that no one knows the carrier status of any individual in the system. In addition to those nine tests, many additional diseases can be picked up by whole genome sequencing. No person can know in advance that they are exempt from these risks.
Furthermore, concerns about rare "false positives" is far less at the stage of matchmaking than at the stage of prenatal testing, since the latter could involve termination of a healthy fetus, while the former just means that you restrict your dating to 90 percent of the population. In order to scale this up from 13 million Ashkenazim and Sephardim to billions in diverse cultures, we will likely see new computer security, encryption, blockchain and matchmaking tools.
Once the diseases are eradicated from our population, the interventions can be said to impact not only the current population, but all subsequent generations.
THE FUTURE
As reading and writing become exponentially more affordable and reliable, we can tackle equitable distribution, but there remain issues of education and security. Society, broadly (insurers, health care providers, governments) should be able to see a roughly 12-fold return on their investment of $1800 per person ($600 each for raw data, interpretation and incentivizing the participant) by saving $1 million per diseased child per 20 families. Everyone will have free access to their genome information and software to guide their choices in precision medicines, mates and participation in biomedical research studies.
In terms of writing and editing, if delivery efficiency and accuracy keep improving, then pill or aerosol formulations of gene therapies -- even non-prescription, veterinary or home-made versions -- are not inconceivable. Preventions tends to be more affordable and more humane than cures. If gene therapies provide prevention of diseases of aging, cancer and cognitive decline, they might be considered "enhancement," but not necessarily more remarkable than past preventative strategies, like vaccines against HPV-cancer, smallpox and polio. Whether we're overcoming an internal genetic flaw or an external infectious disease, the purpose is the same: to minimize human suffering. Once the diseases are eradicated from our population, the interventions can be said to impact not only the current population, but all subsequent generations. This reminds us that we need to listen carefully, educate each other and proactively imagine and deflect likely, and even unlikely, unintended consequences, including stigmatization of the last few unprotected individuals.
A doctor pricks the heel of a newborn for a blood test.
Hours after a baby is born, its heel is pricked with a lancet. Drops of the infant's blood are collected on a porous card, which is then mailed to a state laboratory. The dried blood spots are screened for around thirty conditions, including phenylketonuria (PKU), the metabolic disorder that kick-started this kind of newborn screening over 60 years ago. In the U.S., parents are not asked for permission to screen their child. Newborn screening programs are public health programs, and the assumption is that no good parent would refuse a screening test that could identify a serious yet treatable condition in their baby.
Learning as much as you can about your child's health might seem like a natural obligation of parenting. But it's an assumption that I think needs to be much more closely examined.
Today, with the introduction of genome sequencing into clinical medicine, some are asking whether newborn screening goes far enough. As the cost of sequencing falls, should parents take a more expansive look at their children's health, learning not just whether they have a rare but treatable childhood condition, but also whether they are at risk for untreatable conditions or for diseases that, if they occur at all, will strike only in adulthood? Should genome sequencing be a part of every newborn's care?
It's an idea that appeals to Anne Wojcicki, the founder and CEO of the direct-to-consumer genetic testing company 23andMe, who in a 2016 interview with The Guardian newspaper predicted that having newborns tested would soon be considered standard practice—"as critical as testing your cholesterol"—and a new responsibility of parenting. Wojcicki isn't the only one excited to see everyone's genes examined at birth. Francis Collins, director of the National Institutes of Health and perhaps the most prominent advocate of genomics in the United States, has written that he is "almost certain … that whole-genome sequencing will become part of new-born screening in the next few years." Whether that would happen through state-mandated screening programs, or as part of routine pediatric care—or perhaps as a direct-to-consumer service that parents purchase at birth or receive as a baby-shower gift—is not clear.
Learning as much as you can about your child's health might seem like a natural obligation of parenting. But it's an assumption that I think needs to be much more closely examined, both because the results that genome sequencing can return are more complex and more uncertain than one might expect, and because parents are not actually responsible for their child's lifelong health and well-being.
What is a parent supposed to do about such a risk except worry?
Existing newborn screening tests look for the presence of rare conditions that, if identified early in life, before the child shows any symptoms, can be effectively treated. Sequencing could identify many of these same kinds of conditions (and it might be a good tool if it could be targeted to those conditions alone), but it would also identify gene variants that confer an increased risk rather than a certainty of disease. Occasionally that increased risk will be significant. About 12 percent of women in the general population will develop breast cancer during their lives, while those who have a harmful BRCA1 or BRCA2 gene variant have around a 70 percent chance of developing the disease. But for many—perhaps most—conditions, the increased risk associated with a particular gene variant will be very small. Researchers have identified over 600 genes that appear to be associated with schizophrenia, for example, but any one of those confers only a tiny increase in risk for the disorder. What is a parent supposed to do about such a risk except worry?
Sequencing results are uncertain in other important ways as well. While we now have the ability to map the genome—to create a read-out of the pairs of genetic letters that make up a person's DNA—we are still learning what most of it means for a person's health and well-being. Researchers even have a name for gene variants they think might be associated with a disease or disorder, but for which they don't have enough evidence to be sure. They are called "variants of unknown (or uncertain) significance (VUS), and they pop up in most people's sequencing results. In cancer genetics, where much research has been done, about 1 in 5 gene variants are reclassified over time. Most are downgraded, which means that a good number of VUS are eventually designated benign.
While one parent might reasonably decide to learn about their child's risk for a condition about which nothing can be done medically, a different, yet still thoroughly reasonable, parent might prefer to remain ignorant so that they can enjoy the time before their child is afflicted.
Then there's the puzzle of what to do about results that show increased risk or even certainty for a condition that we have no idea how to prevent. Some genomics advocates argue that even if a result is not "medically actionable," it might have "personal utility" because it allows parents to plan for their child's future needs, to enroll them in research, or to connect with other families whose children carry the same genetic marker.
Finding a certain gene variant in one child might inform parents' decisions about whether to have another—and if they do, about whether to use reproductive technologies or prenatal testing to select against that variant in a future child. I have no doubt that for some parents these personal utility arguments are persuasive, but notice how far we've now strayed from the serious yet treatable conditions that motivated governments to set up newborn screening programs, and to mandate such testing for all.
Which brings me to the other problem with the call for sequencing newborn babies: the idea that even if it's not what the law requires, it's what good parents should do. That idea is very compelling when we're talking about sequencing results that show a serious threat to the child's health, especially when interventions are available to prevent or treat that condition. But as I have shown, many sequencing results are not of this type.
While one parent might reasonably decide to learn about their child's risk for a condition about which nothing can be done medically, a different, yet still thoroughly reasonable, parent might prefer to remain ignorant so that they can enjoy the time before their child is afflicted. This parent might decide that the worry—and the hypervigilence it could inspire in them—is not in their child's best interest, or indeed in their own. This parent might also think that it should be up to the child, when he or she is older, to decide whether to learn about his or her risk for adult-onset conditions, especially given that many adults at high familial risk for conditions like Alzheimer's or Huntington's disease choose never to be tested. This parent will value the child's future autonomy and right not to know more than they value the chance to prepare for a health risk that won't strike the child until 40 or 50 years in the future.
Parents are not obligated to learn about their children's risk for a condition that cannot be prevented, has a small risk of occurring, or that would appear only in adulthood.
Contemporary understandings of parenting are famously demanding. We are asked to do everything within our power to advance our children's health and well-being—to act always in our children's best interests. Against that backdrop, the need to sequence every newborn baby's genome might seem obvious. But we should be skeptical. Many sequencing results are complex and uncertain. Parents are not obligated to learn about their children's risk for a condition that cannot be prevented, has a small risk of occurring, or that would appear only in adulthood. To suggest otherwise is to stretch parental responsibilities beyond the realm of childhood and beyond factors that parents can control.