7 Going On 70: A Barbara Walters Special

Lindsay Ratcliffe of Flat Rock, Mich., lives inside a body that is biologically older than that of her grandmother. The 7-year-old is one of 80 known children who suffer from progeria, an extremely rare and fatal disease characterized by rapid aging in children. It occurs in 1 of every 4 to 8 million births around the world, according to the Progeria Research Foundation.

(Donna Svennevik/ABC)