According to the news, this 9-month-old baby is KJ, the patient who was born with a rare metabolic disease known as severe carbamoyl phosphate synthetase 1 (CPS1) deficiency. This deficiency leads to a buildup of ammonia in the blood, causing brain damage and often death in affected children ².

To treat KJ, researchers corrected a specific gene mutation in the baby’s liver cells that caused the disorder. This historic medical breakthrough could “provide a pathway for gene editing technology to be successfully adapted to treat individuals with rare diseases for whom no medical treatments are available” ². The treatment, which received FDA approval, involved administering low doses of the therapy to KJ, starting when he was six months old, with subsequent larger doses in the months following. The infant has shown no serious side effects and is now able to eat more protein than before ⁴.