But within months, KJ's name ' and megawatt, chubby-cheeked smile ' would be splashed across newspapers and broadcasts around the world as the first known person to receive a personalized CRISPR-based genome-editing therapy. Soon after KJ was born in August 2024, doctors noticed that he was sleeping too much and eating too little. After a bevy of tests, they found that KJ has an ultra-rare genetic condition, called carbamoyl-phosphate synthetase 1 (CPS1) deficiency, that impairs the body's ability to process protein. When the body breaks down proteins, it produces ammonia ' a toxic substance that is usually processed by enzymes in the liver and excreted in urine. CPS1 deficiency compromises one of these enzymes, causing ammonia to accumulate in the blood, which can eventually damage the brain. The condition can be treated with a liver transplant, but about half of all babies with CPS1 deficiency die in early infancy. One of KJ's doctors, paediatrician Rebecca Ahrens-Nicklas at the...
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