The Rarest of All Diseases Are Becoming Treatable

In February, a six-month-old baby named KJ Muldoon became the first person ever to receive a CRISPR gene-editing treatment customized specifically for his unique genetic mutation, a milestone that researchers say marks a turning point in how medicine might approach the thousands of rare diseases that collectively affect 30 million Americans. Muldoon was born with a type of urea-cycle disorder that gives patients roughly a 50% chance of surviving infancy and typically…