We all grow old. But children with progeria, a rare genetic disorder that accelerates aging at an unforgivably aggressive pace, get old before they’ve even tasted youth. They are real-life Benjamin Buttons, with weakened blood vessels and bones that become brittle before they’ve reached middle school. Most die in their teens.

Sam Berns, 13 when he first appears in Life According to Sam, is one of those children. But this documentary, directed by Academy Award-winning D.C. filmmakers Sean Fine and Andrea Nix Fine, isn’t just Sam’s story. It’s also the story of his mother’s efforts to get FDA approval for a drug that could prolong her son’s life and the lives of others who deal with the same cruelly random condition. And it’s the story of how Sam’s parents build a normal life around their beloved, fragile boy, filling it with the classic stuff of American families—baseball games, marching band practice, Dave Matthews Band concerts—while confronting a syndrome so uncommon, it affects just one in four million.

The movie, which debuted at Sundance and airs on HBO this fall, mines most of its suspense from the lengthy progeria drug trial spearheaded by Dr. Leslie Gordon, Sam’s mom. As she waits anxiously to learn whether her study will be published and earn FDA review, so do we. But Life According to Sam isn’t mere medical drama. It’s also a heart-tugging reminder of how hardship can be morphed into a blessing. “I’m sorry it happened to her son,” says the teary-eyed mother of a Canadian progeria patient, referring to Gordon. “But we kind of needed her.”