William’s Story: Gene Replacement Therapy for SMA Type 2

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Amanda and William’s second child, William Jr., was healthy and reaching the expected developmental milestones. Then, at 9 months old, something changed. William showed little interest in moving or trying to crawl and was unable to support his own body weight.

William “His legs were like Jello,” recalls Amanda. “Something didn’t seem right.”

When William turned 1, he still wasn’t crawling or walking and struggled to sit up. The family’s pediatrician recommended early intervention, assuring them that their son’s gross motor delays would likely be resolved in a few weeks. But after a few months of early intervention and no improvement, the pediatrician was concerned and referred the family to the Division of Neurology at Children’s Hospital of Philadelphia (CHOP).

CHOP Pediatric Neurologist Elizabeth Kichula, MD, PhD, evaluated William and immediately suspected spinal muscular atrophy (SMA), a progressive neuromuscular disorder that destroys muscle-controlling nerve cells called motor neurons. Without motor neurons, the body can’t send signals to muscles, which then weaken and become smaller because of inactivity. SMA can affect a child's ability to crawl, walk, sit up, and control head movements, and it can also damage the muscles used for breathing and swallowing. A detailed genetic analysis confirmed that William had SMA.  He was diagnosed with SMA type 2, as he had attained the ability to sit. Untreated, children with SMA type 2 will never be able to walk, and often develop feeding and respiratory issues. 

Amanda and William Sr. were devastated.

“It didn’t feel real,” recalls Amanda. After a few days in mourning, the couple resolved to help their son in any way they could. “We sprang into action mode, committed to doing everything we can to make sure he has the best life.”

Fortunately, a promising SMA treatment — nusinersen — had recently been approved by the FDA. Just a few months later, a gene replacement therapy was approved by the FDA for treatment of children under age 2 with genetically confirmed SMA. Clinical trials of the gene therapy have shown a decreased need for respiratory support as well as improvement in motor skills in young children with SMA. The earlier children receive the gene therapy, the better the results. 

Within a month of receiving the one-time dose of gene therapy, William went from being unable to roll over or lift his arms, to being able to lift his arms over his head and bear weight on his legs. He has continued to gain strength and hit milestones like crawling, standing by himself and taking steps.

We thought our son would never walk, and now here we are, literally 15 months later, and he’s taking steps,” says Amanda, in awe. “It’s been a whirlwind, but everybody on CHOP’s SMA team has been amazing helping us get through this, and he’s doing so well.

Having a child with such a rare condition can be an isolating experience. To remedy that, the CHOP care team connected the couple to another patient family whose child is a month younger than William Jr.

“We have a huge family and we are very close with them. They want to support us, but they aren’t living the day to day that we are,” says Amanda. “Being able to talk to another mom who was going through the same thing made me feel like we weren’t alone and gave me an overwhelming feeling of comfort. That was a good day. I remember driving home from CHOP feeling so good.”

William wearing his leg braces “It’s a great way to connect families, but it’s not something every hospital does,” adds Amanda, noting that since then, the family’s support network outside of their care team has continued to grow. “CHOP did that intentionally for us. It’s just another thing that we’ll be very grateful for always.”

William's story demonstrates the importance of early clinical suspicion, to help start treatment quickly. Newborn screening for SMA is now done in many states, including Pennsylvania and Delaware, in order to help identify the disorder before any symptoms are present. However, this testing only identifies those with the common deletion, and will miss 4% of cases, including William's, where SMA is caused by a deletion in one copy of the gene and an insertions, deletions or point mutation in the other copy. This is an important reminder that even as newborn screening becomes more wide spread, early clinical suspicion is still of utmost importance.

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