A custom gene-editing therapy helped a baby with a rare genetic disease survive. Experts say it could soon revolutionize treatment for millions more.
Hope in a Vial: How Gene Editing Saved One Baby’s Life
In a breakthrough that could change the future of rare disease treatment, a baby diagnosed with a life-threatening genetic disorder is now thriving — thanks to a custom-built gene-editing therapy.
Little KJ Muldoon of Pennsylvania is among the first patients to benefit from an experimental precision therapy designed specifically to correct a deadly mutation in his DNA. His case could open the door for similar treatments for millions of patients with rare and previously untreatable genetic conditions.
The Diagnosis: One-in-a-Million Genetic Disorder
Shortly after birth, KJ was diagnosed with CPS1 deficiency, a rare disorder that prevents the body from eliminating toxic ammonia. The condition, which affects about one in a million newborns, is often fatal, with liver transplantation being one of the few available options.
Faced with grim odds, KJ’s parents, Kyle and Nicole Muldoon, made the courageous decision to try something never attempted before: a gene-editing therapy tailored exclusively for their son.
“We prayed, we talked to people, we gathered information,” said Kyle. “Eventually we decided this was the path we would take.”
A Revolutionary Treatment: Precision Base Editing
Researchers at the Children’s Hospital of Philadelphia (CHOP) and Penn Medicine, using a cutting-edge form of CRISPR gene editing known as base editing, engineered a treatment to flip a single faulty DNA base in KJ’s genetic code. Unlike traditional CRISPR, which cuts DNA, base editing minimizes collateral damage by making precise, chemical-level changes.
By February, the team had delivered the first infusion of the therapy using lipid nanoparticles — tiny fat droplets that target liver cells. KJ peacefully slept through the milestone moment while his care team celebrated a potential medical first.
A Promising Recovery: Small Victories, Big Impact
KJ’s health began improving following his infusions in February, March, and April. He’s now eating more normally, bouncing back from common illnesses, and needing fewer medications.
Considering the bleak prognosis early on, even the smallest milestones — waving, rolling over, or a smile — are celebrated as major victories by his parents.
Dr. Rebecca Ahrens-Nicklas of CHOP, who helped lead the effort, remains cautiously optimistic: “Every day, he’s showing us signs that he’s growing and thriving.”
Wider Impact: A New Era for Rare Disease Treatment
KJ’s case isn’t just remarkable for its success — it’s significant because it demonstrates that custom therapies may soon become more practical and affordable.
Dr. Kiran Musunuru, co-author of the study published in the New England Journal of Medicine, believes this is the start of a larger movement. “This is the first step toward using gene editing to treat a wide variety of rare genetic disorders,” he said.
The treatment’s cost, he added, was comparable to a liver transplant — not the astronomical figure many assume personalized therapies would require. As processes become faster and more efficient, experts believe prices will drop even further.
Looking Ahead: From One Baby to Millions
Though it will take years to fully understand the long-term success of KJ’s treatment, researchers and physicians are optimistic that the lessons learned will pave the way for treating other rare diseases.
“Once someone comes with a breakthrough like this, it will take no time for other teams to apply the lessons,” said Dr. Carlos Moraes, a neurology professor at the University of Miami. “I predict barriers will be crossed in the next five to ten years.”
For now, KJ’s survival is a powerful symbol of what science, hope, and collaboration can achieve — and a glimpse into a future where no rare disease is too rare to treat.
