Three in 10 children with a rare disease do not reach the age of 5. After Mila was diagnosed with Batten disease, Dr. Timothy Yu at Boston Children’s Hospital used a piece of genetic code to engineer a drug customized to Mila’s unique mutation. The drug slowed the progression of the disease and relieved many of its symptoms. Sadly, however, Mila died in February 2021 at the age of 10. Today, Mila’s mother is working to advance custom medicines like the one developed for her daughter.