The baby saved from a rare disease by a first-ever personalized gene fix has reached a big milestone, taking his first steps ahead of Christmas. KJ Muldoon is walking and getting ready to celebrate ...

KJ Muldoon received the first-of-its-kind gene therapy for a potentially fatal disease and is now marking major developmental milestones.

A miracle baby who was treated with a pioneering gene-therapy at CHOP has reached a major milestone as he took his first ...