Mark Johnson and Kathleen Gallagher, reporters for the Milwaukee Journal Sentinel, won the Pulitzer Prize for explanatory journalism in 2011 for reporting on a little boy in Wisconsin with a devastating illness and the doctor and scientists who tried to save him, ultimately opening the door to a new era in genetic medicine. Now, they have expanded on that compelling story in their new book One in a Billion: The Story of Nic Volker and the Dawn of Genomic Medicine (Simon & Schuster). Mark Johnson answered questions from The National’s Kate N. Grossman.

Q: Broadly speaking your book is about pioneering work in genomic medicine and the development of personalized medicine. But it’s also an intimate, human story — an intensely personal look at the life-and-death struggles of a little boy named Nic Volker. Did you go looking for a medical odyssey story to tell or did it all begin with Nic?

It began with Nic. My co-author Kathleen Gallagher had gotten a tip about a child at Children’s Hospital of Wisconsin who had had all of his genes sequenced and they’d found a mutation that had never been seen before, but we didn’t have a name.

Q: And once you learned that Nic was that child, what drew you to the story — the boy himself or the medial breakthrough?

The first thing was that this was a potentially game changing medical treatment. Ever since the Human Genome Project, there’s been this idea out there that knowledge of the genome could be used to save people’s lives. Yet in the years following the Genome Project, there had been more work done on things like sequencing the genome of chocolate or the genomes of fruit flies or yeast. It hadn’t yet crossed that threshold to become human medicine.

Nic’s case turned out to be ideal in a number of ways. The first main draw was that it was potentially a medical landmark. But it was also very important that we had the family because many times with medical landmarks, you get this anonymous patient zero type of person. The family doesn’t want to talk. In this case, it was crucial that the family was willing to talk, because to understand why doctors and scientists used something that hadn’t been used before— genetic sequencing. You had to really know what this child and this family had been through the previous two years — all these tests, and dead ends that hadn’t produced a diagnosis.

Q: Why do you think Nic’s family agreed to share their story – the most intimate details of a period of their lives when they were at their most vulnerable?

As time went on, Kathleen and I both began to realize that the family’s main reason for sharing their story was that at the time that we were talking to them, it was still very uncertain what would happen to Nic. They had a diagnosis but he hadn’t yet begun to receive treatment. His family wanted as many people as possible to know about his medical situation in case something went wrong.

They wanted him to be well enough known that, for example, if his health took a turn for the worse, some doctor at Harvard or in Japan might read about him and say ‘Oh my gosh, I had a patient with very similar symptoms and this is what helped in his case.’ They saw this as a way to reach as many doctors and researchers as possible.

Q: You write in the book about the ethical dilemmas that can and do accompany DNA sequencing of patients like Nic and others. What dilemmas do you think pose the greatest challenges to patients and doctors?

Two things come immediately to mind. One is that when they sequence your genome to find one thing, they can find other incidental conditions. Say you have some problem with your liver and they sequence genes to look for liver problems and they find some other mutation that, for example, means you’ll have Alzheimer’s disease or Parkinson’s. How do you handle that?

It may be different for different people, and it may be different depending on age. Do you want to tell a seven-year-old child that they have a gene that predisposes them to Alzheimer’s? It’s still kind of a new territory and there is not yet a prescribed way to do this. A lot of places have started in the last few years to develop policies but there are still different approaches from hospital to hospital.

I think the idea that most of them stress is that they want parents and families to be in the driver’s seat. But that means that it should be up to them to choose what they want to know and what they don’t want to know. And there are some people that definitely won’t want to know certain things. If your family has a history of breast cancer and we know that mutations on these two genes, BRCA1 and BRCA2, really increase your odds of getting breast cancer, there may one sister who doesn’t want the knowledge and another sister who says ‘I’d rather know and plan my life accordingly.’

The second big ethical question surrounds telling parents and patients about mutations we don’t understand. One thing that I hadn’t realized, and I think many members of the general public don’t either, is that we still don’t know what most genes do. We now have this new tool that will help us determine if we don’t have the sequence we should for a particular gene, but unless we know what that gene is supposed to do, it’s pretty hard to know how that mutation will play out in terms of our actual health.

That opens up some other questions too. For really complex illnesses, like heart disease or diabetes or obesity, certain mutations don’t mean you’ll get it, but they increase your risk. And it’s not always by tidy numbers, like by 70 percent. Potentially, a mutation could increase your risk by 13 percent. What does a doctor do with that? Do you tell your patient and have them potentially worry a great deal? Is there actual medical advice to go with that? Do you tell them, ‘Hey, watch your diet, from now on no pizza.’ It’s much easier to tell a person what a particular mutation does than to tell a patient what they should do about it.

Q: Your book began as a three-part series in the Milwaukee Journal Sentinel, where both you and your co-author Kathleen Gallagher work. How did you transform that series — which won the Pulitzer Prize for explanatory journalism in 2011 — into a 202-page book?

For both Kathleen and me, this was our first book and we were kind of waking into it blindly. We talked to others who had done it. But a lot of the work of it, lots of the experiences, you just have to run into them by yourself. We had been very organized for the series. We did most interviews on tape and we typed up transcripts. We kept maybe a dozen binders on different topics full of things. We thought we’d be in great shape for a book.

Then you have to look at things in a different way to write a book – character development becomes much more important. We really had to go into backstories in a much more detailed way. It was incredibly rewarding because we found out things that we hadn’t known for the series.

For example, Nic’s main doctor, Alan Mayer, he’s the son of two Holocaust survivors. That detail actually shaped a lot of his approach to medicine and to life. He’s a guy who sort of kind of calculates odds and thinks about probabilities and statistics. It actually influenced the way that he saw his interactions with Nic. There were times when he really looked at it as a phenomenal long shot that he was even born to be here when this child had this medical crisis. It kind of made for a theme in the book — fate and chances and probability. There were numerous other things we came across that we had no idea about when we did the newspaper series.

Q: Without giving too much away, there is a great mystery in the book — will Nic survive? Why did you set up the book with that mystery at its core?

I write a decent number of narrative stories and one of the things I was taught early on was that for a successful narrative, you need an engine, something driving the story forward. Usually, it’s a question. In this case, the question is the most basic one — will Nic survive?

There are other questions, but they are all in the service of that question. For scientists, the big question was would this technique work? Would the equipment work as it was supposed to? Then a secondary question: Would it help them find an answer? Then a third question was: Would getting the answer, the diagnosis, actually help cure Nic?

For the family, only the last question mattered. And for most people, that was the question they could most easily identify with as they read along. That was why we chose Nic’s survival as the engine for the story.

Q: You spend a lot of time in the book describing the medical institutions involved — the Medical College of Wisconsin and Children Hospital of Wisconsin. What made them such important characters in this story?

This turned out to be a really good underdog story because this breakthrough didn’t take place at one of the huge sequencing centers like MIT, Baylor College of Medicine or Washington University in St. Louis. Many of those places have dozens of sequencing machines. This happened at the Medical College of Wisconsin and Children’s Hospital of Wisconsin, where they only had one sequencing machine and weren’t considered to be at the highest level of genetics experts. And it turned out it didn’t happen by accident. This relatively small institution had done a smart thing — they’d been planning a long time for this particular development.

Q: When it was all said and done how did the family respond to the book?

They liked it. Nic’s mom has appeared with us at a couple of talks we’ve done. She’s started the Nicholas Volker One in a Billion Foundation to get more awareness of the use of genomic medicine and to maybe get it used with children much earlier.

The lesson that they took away with what happened with their son was that he really suffered for three to four years until this treatment actually told doctors what was going on, until it helped them understand the problem. They felt if his genes had been sequenced much earlier it could have saved him a lot of suffering.

There is talk of doing this now — a child would be sequenced at birth, then if a potential problem shows up, especially something a little strange or baffling, they could go right to this blueprint for all of the child’s genes and look for obvious clues, something that seems unusual in his genome.

This interview was edited for publication.