One-of-a-kind treatment gave baby KJ a shot at a healthy life

Within minutes of KJ Muldoon’s birth, doctors knew there was something very wrong.

Five weeks premature, his little arms went rigid when lifted and shook oddly on the way back down.

An attentive doctor at the University of Pennsylvania, checking for a host of possible causes, noticed that KJ’s ammonia level was off the charts.

He was rushed across the street to Children’s Hospital of Philadelphia, where doctors quickly offered a dire diagnosis. His body couldn’t clear ammonia, which is produced when the body turns protein from food into energy. Without being able to urinate it out, like healthy people do, the ammonia would build up and damage first his brain and then his whole body.

By day two of KJ’s life, his parents Kyle and Nicole were getting the worst possible news: “I heard ‘death’ or ‘severely developmentally disabled.’ There wasn’t really a whole lot of getting around that,” Kyle remembered.

Yet nine months later, KJ is smiling, sitting up unassisted and – on one recent day – happily eating avocado. “He’s defeated all odds and obstacles so far that were put in his way. He exceeds our expectations,” Nicole said in a May 12 call with reporters.

All this is possible because KJ is the first-ever recipient of a gene therapy designed to treat only a single person.

Every month for the past three, he’s received an infusion of billions of tiny balls of fat, containing instructions to edit genes in his liver cells. Fixing the genetic mistake in at least some of his liver cells enables his body to make an enzyme called CPS1, which is needed to break down protein. KJ’s ammonia level is now pretty close to normal.

Doctors say it’s too early to declare KJ “cured” or know what the rest of his life will look like. But he’s definitely on a better trajectory than when Nicole and Kyle, who have three older children, were told the best they could hope for was to minimize KJ’s suffering.

“Seeing him reach milestones that are important for any infant as they’re developing blows us away even more because we know what was stacked up against him and how bad of a prognosis it was in the very beginning,” said Nicole, 34 of Clifton Heights, Pennsylvania.

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