This Baby Was Saved by a One-of-a-Kind Gene Editing Treatment

For the first time in history, doctors created a one-patient CRISPR gene therapy to save a life. Baby K.J. Muldoon was born with a rare condition that prevented his body from properly processing ammonia — a potentially fatal genetic error.

Dr. Rebecca Ahrens-Nicklas of the Children’s Hospital of Philadelphia and Dr. Kiran Musunuru of Penn Medicine developed a custom CRISPR treatment tailored to K.J.’s DNA. The therapy edited a single gene to correct the error, stabilizing his condition. This breakthrough opens the door to a future where bespoke gene editing could save thousands living with ultra-rare disorders.