A 7-year-old is fighting off a rare, life-threatening genetic disease — with his own cells

At just 7 years old, Caleb McMillan has been through a lot. Caleb has a diagnosis of an extremely rare, life-threatening condition called cerebral X-linked adrenoleukodystrophy, or CALD. The disease took the life of Caleb’s cousin, Evan, when he was just 9 years old, pushing Caleb and his brother Tyler to both get tested. Both boys ended up having the genetic mutation that could lead to CALD.

In December of last year, Caleb’s lesions began to appear. Teams of doctors and specialists led them to Boston from their home in Ohio, and he’ll be undergoing a new type of gene therapy at Mass General: Skysona, a treatment approved by the FDA last fall, that could save his life. Caleb’s parents, Shauna and Lonnie McMillan, joined GBH’s All Things Considered host Arun Rath to tell Caleb’s story, share each step of the journey and explain where they’ll go from here.

Arun Rath: Shauna, take us back to when you decided to take your boys to be tested. Had you ever heard about this disease before what happened with Caleb’s cousin, Evan?

Shauna McMillan: Well, kind of, but not really. When I was eight years old, I watched [the movie] “Lorenzo’s Oil,” and it was about a little boy with ALD. So back in the past, I had heard of it, but I never imagined it would have affected our family like this. It all just kind of flashed back.

With this diagnosis, we just right away knew with it being an X-linked disorder, I could have inherited it and passed it on. So right after we had suspicions and genetic testing back for Evan, we had both of the boys immediately tested. After about two weeks, we had our results back, and we were able to confirm the diagnosis.

Rath: As a parent, it’s hard for me to get my mind around what that would be like. You can’t be paralyzed, so what do you do from there?

Lonnie McMillan: We were fortunate enough to be put in touch with some other people who had gone through this. We learned pretty quickly about what the whole journey would be like. There’s a lot of different ways that it can go.

Every six months, they have to get MRIs to make sure that nothing shows up. For our other son, Tyler, it’s come back clean every time, but for Caleb, back in his December MRI, we found out, which was the most difficult thing.

Courtesy of Shauna McMillan

Rath: Tell us about the path that led you to Massachusetts, to what could be a potentially life-saving treatment here.

Shauna: In 2018, our geneticist recommended: the only way to stop this from forming was a bone marrow transplant. But for a small group of boys, there aren’t any available donors. Our geneticist recommended that we do this testing in advance to kind of have an idea, if the boys develop a cerebral form of the disease. In 2018, we had them both tested. Tyler, again on the lucky side, had 230 matches. Caleb had none.

So we followed up to see what our options were. We were, at the time, following some gene therapy clinical trials that were going on, so that became a reality once we knew that Caleb would not have a match. We knew that the only option for him would be this gene therapy.

Thankfully, in September of 2022, it was approved by the FDA. Following his MRI in December, we knew right away that we were going to have to go this route. Having followed the study, we knew that it was only available in Boston and Philadelphia, so that was what began our path.

After that, there were several phone calls between our doctors, communicating back and forth. Then, in March, they brought us out to do another MRI to make sure the disease was progressing; every now and then, it’ll show up, and then it’ll just halt. From there, we arrived in Boston last Tuesday, and we had doctor’s appointments. On Monday, he was admitted to Boston Children’s, where they put in a tube that harvests the white blood cells that they will send for the therapy to be created.

Rath: That’s amazing. And he was discharged?

Shauna: We had a very successful harvest. Typically, the kids are on the machine for about six hours. He was kind of borderline in terms of whether or not they would have the cells, so they proactively said, “Let’s go for two more hours.” So he was hooked up to the machine for eight hours.

Rath: It’s incredible, using his own cells to heal.

Shauna: It’s pretty amazing. In 8 to 10 weeks, those cells will be ready, and they’ll send them back.

Rath: Had it not been for the tragedy with his cousin, you wouldn’t have had any reason to think to test your boys. Should screening for this be more widespread?

Shauna: Oh, absolutely. There is a community right now trying to get newborn screenings in every state. The earliest detection is essential for keeping this managed, for the best outcome for the kids.

Lonnie: If it weren’t for us knowing, it would have been the same result for Caleb. If we found it too late, there would have been nothing that could have been done. Kids have a chance if they know what they’re up against before it takes their life away.

Shauna: It’s a very risky procedure. Obviously, a gene therapy transplant like this has a lot of components. It’s the only thing available right now to stop this disease, so just being aware is absolutely essential for the best outcomes.

Lonnie: And for Caleb’s specific case, the fact that this gene therapy is available is truly amazing, especially the timing of it. A coupe of years ago, we may have been able to get it done through a clinical trial, but beyond that, it really would have been limited options.

You probably would have had to go through with the bone marrow, and with him not having a good match, it really wouldn’t have been a good option if therapy hadn’t been developed. Fortunately, it came just in time.