A baby in Pennsylvania has improved after getting a special new treatment. The baby was born in Pennsylvania with a rare illness called CPS1 deficiency. This illness is very dangerous. It affects about one baby in a million. It stops the body from removing ammonia. Ammonia can make the body very sick or even be life-threatening. In February 2025, doctors at a hospital in Philadelphia gave the baby a new kind of medicine. The doctors made this medicine in six months. It used a method called “base editing.” This method is part of a gene-editing tool called CRISPR. It changes a small part of the baby’s DNA without cutting it. It helps fix the problem in the body safely.

The medicine was sent into the baby’s body using tiny fat particles. These particles carry the medicine to the liver. After a few treatments, the baby started to eat better and get well from small sicknesses. Doctors said this new treatment is fast, safe, and helpful. It may help other people with rare illnesses in the future. The price is about the same as a liver transplant. Experts hope this new method will be easier for more people to use one day.