From the moment Adam was born in 2020, his parents, Mary Beth and Dave, were thrust into a situation they never anticipated: Caring for a child with a rare disease. Newborn screening revealed that Adam had severe mucopolysaccharidosis type I (MPS I), a lysosomal storage disorder also known as Hurler syndrome. The condition causes build-up of various toxic materials in the body’s cells. 

In severe MPS I, the disease can affect facial features and skeletal development as well as cause developmental delays within the first year or two of life. Other symptoms can include an enlarged head, cornea issues, hearing loss, recurrent infections, enlarged organs, heart disease and more. Without treatments that alter the course of the disease, children with severe MPS can suffer organ damage, progressive cognitive decline and a substantially reduced life expectancy.

At 6 weeks old, Adam began weekly enzyme replacement infusions. This therapy can improve symptoms but has limitations, particularly regarding brain function. By the time Adam was 4 months old, his care team at Children’s Hospital of Philadelphia (CHOP) recommended a bone marrow transplant, which infuses healthy stem cells into the body to replace diseased or damaged bone marrow. This procedure would be the best early chance to preserve Adam’s brain.

After a few months, however, it was clear the transplant was failing. Faced with the prospect of a second, more toxic transplant, his family and care team began to weigh alternatives. 

A transformative option: gene therapy

In May 2021 at 13 months old, Adam was enrolled in a gene therapy clinical trial at CHOP. The day after dosing, his mother remembers a light coming on in his eyes — “It was an alertness we had never before observed.” Over the next months and years, more changes unfolded: a budding love of letters and sign language, reading at 3, and by 5 an insatiable curiosity about the world. “His cognition is in a much healthier place than it would have been without the gene therapy treatment,” says Mary Beth. 

“Thanks to early identification, the subsequent bone marrow transplant and the gene therapy treatment, Adam’s cognitive development was preserved, allowing him to perform far above expectations — reading well, loving math and scoring in the 99th percentile for his age — outcomes that would have been highly unlikely without these interventions,” says Rebecca Ahrens-Nicklas, MD, PhD, a pediatric geneticist and Director of CHOP’s Gene Therapy for Inherited Metabolic Disorders Program, who is also Adam’s doctor.

The importance of long-term monitoring

In June 2025, Ahrens-Nicklas discovered a lesion on Adam’s brain, and he was immediately admitted to CHOP for surgery to remove it, followed by a second operation in August to excise the remaining portion. The team continues close surveillance, following up with Adam every three months with brain and spine MRIs.

Now 6 and in kindergarten, Adam brightens every room with his curiosity. He continues to receive ongoing enzyme infusions, regular MRIs, and specialty care for the orthopedic and developmental challenges of MPS I, with future procedures already planned as part of his long-term management.

There is molecular evidence that pieces of the gene therapy’s delivery system were associated with development of the tumor (read CHOP’s press release about Adam’s case). Nevertheless, his mother’s message is simple and urgent: Gene therapy gave Adam time and cognitive abilities that have changed their lives. While safety must be the first concern, families living with a rare, progressive disease need the option to access game-changing treatments such as gene therapy.

“Knowing what we know now, we would choose gene therapy again,” said Mary Beth. “It gave our son a chance to live, to learn and to truly thrive. Having had to sit in a room and be told that your child has a terminal illness, your perspective in life changes. Given any option to extend your child’s life and to give them a better quality of life makes all the difference.”

Throughout the family’s journey, even during the hardest moments, says Mary Beth, “Watching Adam laugh, discover and grow has made the risk worth taking.”