Home for Christmas: Baby treated with world-first CRISPR therapy takes first steps

After a groundbreaking gene therapy, a baby born with a deadly disorder is reaching milestones once out of reach. KJ Muldoon walking CHOP A year ago, doctors did not know if KJ Muldoon would survive infancy. Today, he is learning to walk at home with his family. His first steps follow a medical first that changed the course of his life.

Earlier this year, physicians at the Children’s Hospital of Philadelphia treated KJ with a one-patient CRISPR gene-editing therapy. The personalized treatment targeted a rare metabolic disorder that often proves fatal in babies. KJ became the first person in the world to receive this type of customized gene-editing care. The therapy helped move his life beyond hospital rooms and constant monitoring.

After spending most of his first ten months admitted for care, doctors discharged him in June. Since then, KJ has continued to grow, reach developmental milestones, and experience moments once considered out of reach. Life beyond hospital walls The therapy changed more than KJ’s medical outlook. It reshaped daily life for his family.

After years defined by intensive care units and monitoring equipment, they brought him home. In August, KJ celebrated his first birthday outside a hospital setting. The milestone marked a sharp contrast from the year before, when medical teams managed every aspect of his care. Since returning home, he has reached multiple developmental benchmarks.

KJ recently began taking his first steps. Doctors also report continued progress in other early childhood milestones. Later this month, he will celebrate his first Christmas at home. Last year, the holiday took place in a hospital room.

Physicians say these moments highlight the broader impact of the therapy. The goal extended beyond survival. Doctors aimed to give KJ a chance at a normal childhood. Scientists expand the approach Rebecca Ahrens-Nicklas, MD, PhD, leads the Gene Therapy for Inherited Metabolic Disorders Frontier Program at CHOP.

She continues to work closely with Kiran Musunuru, MD, PhD, at the University of Pennsylvania. Together, they aim to extend the approach used in KJ’s case to other children. The GTIMD Program focuses on inborn errors of metabolism. These disorders disrupt essential chemical pathways in the body.

Many lack effective treatments and require lifelong management. Researchers in the program are studying urea cycle disorders, organic acidemias, and fatty acid oxidation disorders. Each condition presents unique genetic and biochemical challenges. Scientists hope personalized gene -editing tools can address those differences.

Laboratory teams now use KJ’s case as a reference point. His response offers valuable insight into dosing, safety, and long-term monitoring. A regulatory turning point KJ’s treatment also raises broader policy questions. His case involved a therapy designed for a single patient rather than a large trial population.

That approach challenges traditional drug approval models. A recent editorial in the New England Journal of Medicine cited KJ’s experience. The article highlighted lessons from his treatment and their relevance to the rare disease community. Regulators and researchers now debate how to evaluate similar personalized therapies.

For families facing rare metabolic diseases, KJ’s progress offers cautious optimism. His story shows how rapid collaboration between clinicians, researchers, and regulators can change outcomes. In 2025, his growing list of “first” moments stands as evidence of that shift. Get the latest in engineering, tech, space & science - delivered daily to your inbox.

Aamir is a seasoned tech journalist with experience at Exhibit Magazine, Republic World, and PR Newswire. With a deep love for all things tech and science, he has spent years decoding the latest innovations and exploring how they shape industries, lifestyles, and the future of humanity.