A baby in Pennsylvania has shown strong improvement after receiving an experimental gene-editing treatment for a rare and serious disease. The baby was born with CPS1 deficiency, a genetic disorder that affects about one in a million newborns. This condition stops the body from removing ammonia, which can be dangerous and even deadly for infants. In February 2025, scientists at the Children’s Hospital of Philadelphia and Penn Medicine gave the baby a personalized treatment. It was developed in just six months using a technique called “base editing.” This is a new type of CRISPR gene editing that changes one DNA base without cutting the whole strand. Experts say this method reduces the risk of mistakes and may help treat other rare conditions.

The treatment was given through lipid nanoparticles—tiny fat-based particles that bring the therapy to liver cells. After receiving several infusions, the baby’s health began to improve. The child now eats better and recovers from minor illnesses more easily. Doctors say this case shows how customized gene editing can be effective, safe, and fast. Although it is too early to know the long-term results, this success offers hope for patients with other rare diseases. The cost of the treatment is similar to a liver transplant. In the future, scientists hope this method will become more widely available and affordable.