Finally tonight, two, young boys. One of them with a rare disease, with no cure yet. And his best friend, who is just 7 years old, but setting out to change the world. ABC's Steve osunsami, with the... See More
Finally tonight, two, young boys. One of them with a rare disease, with no cure yet. And his best friend, who is just 7 years old, but setting out to change the world. ABC's Steve osunsami, with the friendship that is "America strong." Reporter: It's 3:00 A.M. In California. And 8-year-old Jonah pournazarian has to be fed. It's an anxiety I don't wish on any parent. Ever. Reporter: He needs these precisely measured battles of water and cornstarch through a tube in his stomach. Jonah suffers from a rare liver disorder. That means he's always fighting dangerously low blood sugar. We hope we don't miss him because we could die. His life is in our hands. Reporter: One scientist who has been racing towards a cure, almost ran out of funding. But help is now coming from an unexpected place. Jonah's best friend from preschool. He says his friendship with Jonah is as awesome as a chocolate bar. So, he wrote a book of the same name. I like to help my friend. That's the biggest chocolate bar. Reporter: At $20 a copy, the book has turned into a sweet success. I'm going to take ten of them, then. Reporter: Raising $500,000, from new friends with big hearts in all 50 states and 42 countries. And every cent goes to the Florida lab where they truly believe they're getting closer. It's not just a dream, that these children can be cured. Reporter: 10, 15 years from now, where will the two of you be? High school. High school and probably his disease will be cured. Thank you. Reporter: Just last week, the hospital awarded Dylan for his service. It is all "America strong." And it's as awesome as a chocolate bar. Steve osunsami, ABC news, Gainesville, Florida. It sure is.
This transcript has been automatically generated and may not be 100% accurate.