What is the milestone KJ Muldoon achieved after gene editing?

KJ Muldoon, the first infant to undergo gene-editing therapy, has taken his first steps.

What rare disease did KJ Muldoon have?

KJ Muldoon was diagnosed with a rare metabolic disease called severe carbamoyl phosphate synthetase 1 (CPS1) deficiency.

How does CRISPR gene editing help babies like KJ Muldoon?

CRISPR technology was used to create a custom therapy to correct genetic mutations, offering a potential cure for ultra-rare diseases like KJ's.

Home / Health / Miracle Baby Walks After Gene Editing Therapy

Miracle Baby Walks After Gene Editing Therapy

22 Dec, 2025

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Summary

First infant recipient of gene editing therapy walks at one year old.
KJ Muldoon, diagnosed with rare CPS1 deficiency, spent first 10 months hospitalized.
Therapy developed using CRISPR technology offers hope for rare genetic disorders.

Miracle Baby Walks After Gene Editing Therapy

The first infant to undergo gene-editing therapy, one-year-old KJ Muldoon, has achieved another significant milestone: taking his first steps. This development comes after KJ spent his initial 10 months of life hospitalized due to a rare metabolic disease, CPS1 deficiency. His recovery is being hailed as a miracle by his parents.

The groundbreaking treatment for KJ, who was diagnosed shortly after his August 2024 birth, was developed over six months using CRISPR gene-editing technology. This custom therapy was created by doctors at the Children's Hospital of Philadelphia and the University of Pennsylvania. Previous to this intervention, CPS1 deficiency, affecting 1 in 1.3 million babies, often resulted in life-threatening outcomes, with about 50% of infants dying within the first week.

Following the gene therapy administration in April 2025, KJ showed no serious side effects and was discharged in June 2025, thriving at home. His progress, detailed in The New England Journal of Medicine, is considered highly promising by his medical team. This case is not only a personal triumph for KJ and his family but also paves the way for new discussions on approving personalized therapies for rare diseases, offering hope for many others.