A baby born with a rare and dangerous genetic disease is growing and thriving after getting an experimental gene editing treatment made just for him. Researchers described the case in a new study, saying he’s among the first to be successfully treated with a custom therapy that seeks to fix a tiny but critical error in his genetic code that kills half of affected infants. Though it may be a while before similar personalized treatments are available for others, doctors hope the technology can someday help the millions left behind even as genetic medicine has advanced because their conditions are so rare. “This is the first step towards the use of gene editing therapies to treat a wide variety of rare genetic disorders for which there are currently no definitive medical treatments,” said Dr. Kiran Musunuru, a University of Pennsylvania gene editing expert who co-authored the study published Thursday in the New England Journal of Medicine. The baby, KJ Muldoon of Clifton Heights, Pennsylvania, is one of 350 million people worldwide with rare diseases, most of which are genetic. He was diagnosed shortly after birth with severe CPS1 deficiency, estimated by some experts to affect around one in a million babies. Those infants lack an enzyme needed to help remove ammonia from the body, so it can build up in their blood and become toxic. A liver transplant is an option for some. Knowing KJ’s odds, parents Kyle and Nicole Muldoon, both 34, worried they could lose him. “We were, like, you know, weighing all the options, asking all the questions for either the liver transplant, which is invasive, or something that’s never been done before,” Nicole said. “We prayed, we talked to people, we gathered information, and we eventually decided that this was the way we were going to go,” her husband added. Within six months, the team at Children’s Hospital of Philadelphia and Penn Medicine, along with their partners, created a therapy designed to correct KJ’s faulty gene. They used CRISPR, the gene editing tool that won its inventors the Nobel Prize in 2020. Instead of cutting the DNA strand like the first CRISPR approaches, doctors employed a technique that flips the mutated DNA “letter” — also known as a base — to the correct type. Known as “base editing," it reduces the risk of unintended genetic changes. It’s “very exciting” that the team created the therapy so quickly, said gene therapy researcher Senthil Bhoopalan at St. Jude Children’s Research Hospital in Memphis, who wasn’t involved in the study. “This really sets the pace and the benchmark for such approaches.” Read more: https://www.9news.com/article/news/nation-world/gene-editing-treatment-baby-rare-genetic-disease/507-7e5f9f9c-e919-4a2e-b2c0-bdd1e86efd57 More local videos here: https://youtube.com/@9news Subscribe to NEXT: https://youtube.com/@Nexton9NEWS Stay connected: 9NEWS Website: https://www.9news.com/ Facebook: https://www.facebook.com/ilike9news X: https://x.com/9NEWS Instagram: https://www.instagram.com/9newsdenver/ Download the 9NEWS App: https://www.9news.com/appredirect/ Sign up for the 9NEWSLETTER: https://www.9news.com/email 9NEWS (KUSA) is located in Denver, Colorado.